proper Xaxis design
lazarus / 55-TAChart

----------------------------------------------------------------------
frederic · 2015-02-10 21:25

dear specialist,

i have encoutered propblems in setting up the layout of an x-axis:

ultimate goal :
the labels shown on the x-axis should be  time so     X:XX
once  a day: a date identification      example  06/02/14

so far straigth forward " tdatetime" but  the available chart  data
are available only a period of a day;  say shopping hours (9:00h  to
18:30h) and i want get chart  without the empty spaces of night hours
(in future also no free days or weekends;but that is for further
optimization)

secondly ; i select only data  as only a section out of big file and
want to run a program on this.This requires the need of having the
x-axis setup during a number of days before data starts and also a
number of days after the termination of the available data also
continuing the describted  x-axis setup .

i descided to use lineseries on the basis of x-axis numbers and
making an string array covering the whole x-axis range in datetime
values to provide the mark labels as text.

Code: [Select]
procedure TForm1.inputOKEClick(Sender: TObject);
var n:integer;
begin
       chart1lineseries1.clear;
     Fstartingday:=strtodatetime (startingdate.text);
     Fopeningtime:=strtodatetime (openingtime.text);
     Fclosingtime:=strtodatetime (closingtime.Text);
     Fnumberofdays:=strtoint ( numberofdays.text);
     FextraNODbefore:=strtoint ( extraNODbefore.text);
     FextraNODafter:=strtoint ( extraNODafter.text);
    //determination of size of x-axis array
    XaxisMAXdefinition(Fstartingday,Fopeningtime ,
Fclosingtime,Fnumberofdays,FextraNODbefore,FextraNODafter,Fxaxismax
,Fgrafstartmin,Fgrafclosemin, Fminperday);

    setlength(FXaxDT, Fxaxismax+1);
    setlength(FXaxisstring,Fxaxismax+1);
    setlength(Fxtime,Fxaxismax+1);
    setlength(Fxday,Fxaxismax+1);
   //determination of size of x-axis datetime arrays
   Xaxisdefinition(Fstartingday,Fopeningtime , Fclosingtime,Fnumberofd
ays,FextraNODbefore,FextraNODafter,FXaxDT,Fxtime,Fxday);
    // making the string array
       for  n:=0 to  Fxaxismax do
               begin
                    if n > 0 then
                    begin
                          if Fxday[n]<> Fxday[n-1] then 
FXaxisstring[n]:= '     '+ #13#10 + datetostr(Fxday[n] );
                           if Fxday[n]= Fxday[n-1] then
FXaxisstring[n]:= timetostr(Fxtime [n])//only time    ;
                    end;
               end;
       graf(Fgrafstartmin,Fgrafclosemin);
end;
                                  
de graf procedure
Code: [Select]procedure TForm1.graf(agrafstartmin,
agrafclosemin:integer );
const MIN = -10;
      MAX = 10;
var
 i,ii,N: Integer;
 x,Y: Double;
begin
  N:= agrafclosemin-agrafstartmin;
  Chart1.BottomAxis.Marks.Source := Chart1LineSeries1.ListSource;

  for i:=0 to agrafstartmin- 1 do
 begin
 //   y:=nil;   <-----   does not work
    Y:=1; // arbitrary value : but not wanted
   Chart1LineSeries1.AddXY(i, Y,FXaxisstring[i]);
   end;

 for ii:=0 to N - 1 do
 begin
   x := MIN + (MAX - MIN) * ii / (N - 1);
   Chart1LineSeries1.AddXY(agrafstartmin+ii,
sin(x),FXaxisstring[agrafstartmin+ii]);  // test chart
   end;

   for i:=agrafclosemin to Fxaxismax do
 begin

   Chart1LineSeries1.AddXY(i, 1,FXaxisstring[i]);
   end;

end;                            

in the attached program you see that only the transfer to time labels
has been succesfull. The transfer to datelabels is far from optimal

Code: [Select]can someone give tips to improve the situation?

frederic

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wp · 2015-02-10 22:21

Quote from: fredericattached programThere is no attached program.
Please attach only pas, lfm, lpi and lpr files, the others are not
needed; in particular don't add the exe and the ppus. Pack all files
into a zip which you can upload here. Please add also some sample data
and maybe a sketch of what you want the axis to look like. The
discussion will be much more efficient if I can compile the program.

Are the data points equidistant?

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frederic · 2015-02-11 09:43

wp
i saw that only the last of 4 zips was send
so again

frederic

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frederic · 2015-02-11 10:22

wp
in the attachment a sketch of the x-axis

 the data are equidistant (every minute between the shop opening and
closing time
frederic

----------------------------------------------------------------------
wp · 2015-02-11 12:35

Now I think I know what you mean. Here's a little demo with random
data which I hope covers your specification. It was a bit tricky I
have to confess...

Non-linear axis
The basic problem is that you want to "cut out" the time during the
weekend and the shop's closed hour. This results in a non-linear axis.
In TAChart, non-linear axes are handled by means of
AxisTransformations; there are some pre-built ones, but we need here
the TUserDefinedAxisTransform which gives most flexibility in defining
the transformation by means of OnAxisToGraph and OnGraphToAxis events.

To understand transformations you must know that there are two
coordinate systems involved: one is the coordinate system of the
numbers that appear as labels on the axes - in your case, these are
the date/time values; TAChart calls this "Axis coordinates". The other
coordinate system is the invisible linear coordinate system along the
axes, like in an old-fashioned graph paper; it is called "Graph
coordinates" by TAChart.

The event OnAxisToGraph converts axis units (your date/times) to graph
units in the plot, OnGraphToAxis converts in the opposite direction.

The basic idea with the transformation is as follows:
 In a date/time number, the integer part corresponds to the days, the
fractional part to the time between midnight to midnight.So, if you
want to plot only data during the shop's open hours blow up the range
between 9:00 ( time part = 9/24 = 0.25) and 18:30 (time part = 18.5/24
= 0.77083333) to the range between 0 and 1:t(graph) = (t(axis) - 0.25)
(0.78083333 - 0.25). Similarly with the days: Just count the working
days between the starting date (first date in the plot) and the
current date to be converted and skip the weekends - my demo contains
a function for this ("CountWorkDays")Therefore, the event handler for
OnAxisToGraph can be written as:
Code: [Select]{ Transforms a "date/time" number AX to invisible graph
units }
procedure
TForm1.ChartAxisTransformations1UserDefinedAxisTransform1AxisToGraph(
  AX: Double; out AT: Double);
begin
  AT := CountWorkdays(StartDate, AX) + (frac(AX) - StartTime)/(EndTime
- StartTime);
end;
For the opposite direction, graph to axis, we need the inversion of
CountWorkdays which I called AddWorkDays - it adds a given number of
workdays to a starting date and correctly considers the weekend:
Code: [Select]{ Converts a number which is given in the invisible
graph units to a real
  "date/time" value. }
procedure
TForm1.ChartAxisTransformations1UserDefinedAxisTransform1GraphToAxis(
  AX: Double; out AT: Double);
begin
  AT := AddWorkdays(StartDate, trunc(AX)) +  frac(AX) * (EndTime -
StartTime) + StartTime;
end;   
In order to activate the axis transform, you have to add a
TChartAxisTransformation component onto the form. Right-click and add
a TUserDefinedAxisTransform. Assign above methods to its events.
Assign the AxisTransfor to the Marks.Transformation property of the
bottom axis. And - this is what I always forget - assign the index of
the bottom axis (1) to the AxisIndexX property of the series.

Axis labels
In principle, you could use a TDateTimeIntervalChartSource to convert
the date/time numbers to strings. But his components has a life of its
own, and I never understood how it is working. Therefore I propose to
add a TListChartSource to which you "add" all date/time values and
their string representation at which you want to have a label. This
way you can also take care of the different format: the first label of
a day should show date plus time, the other label only time. In the
demo project, this happens in the method "CreateAxisLabels".

In order to activate these labels you assign this ChartSource to the
Marks.Source property of the bottom axis, and set the Marks.Style to
smsLabel.

In order to check whether the labelling procedure is correct I added
the date/times of each datapoint to the series. You can turn this off
by LineSeries.Marks.Style = smsNone.

----------------------------------------------------------------------
frederic · 2015-02-11 16:20

wp ,
thank you, this is indeed what i was trying to achieve

it looks that ,even when there are no measuring data available, the
x-axis can still be created.

i am going to integrate this solution in my application  where i use
multiple panes to present data simultaneously ; that is  the next
challenge

thank you again

frederic

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frederic · 2015-02-12 21:14

Wp,
I am one step further in using your decribed axis solution.

First I have changed the position of the labels of the axis (from
vertical to horizontal),which means  than the length of the text of
the label becomes important to get consistent results .

As described we will have the date indication at the first mark of
that partical day .
I prefer of having that date markation  at the second level of the
label  for clarity .

The date indication has been changed to 'dd/mm' which total width in
pixels should be equal to the time indication 'hh:mm'. 


 What type of label font should than be used  to achieve this?
(I have choosen labelfont charset  :  default_charset
                           labelfont name : courier)

I added to your project an X-axis zoom and pan procedure and that
worked.
The only problem i see there is that only the first data indication is
consistent and with panning you see very often the date indication
dissappear 
Why is that?

ps
In the attached project I included some setting possibilties like
number of minutes between marks,minimum pixels between  labels and the
zoomfactor . I could ,however,not find a setting to avoid this
dissapearing

frederic

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wp · 2015-02-13 12:41

I am bit confused because you changed something with the program which
moved the x axis labels below the lower edge of the chart and I can't
find what you did... And next time, when you submit code, please pack
all files into a single zip. This help me to create the project easier
and yourself to overcome the file count limitation of the forum.

Please see my modified demo again:

You changed the distance of the x labels to 10 minutes - that's way
too close, all labels are overlapping. You try to avoid this by using
Marks.OverlapPolicy and adapting Axis.Intervals. But when you do this
you lose control over positioning of the labels. When the automatic
label finder algorithm decides that the first day label (the one with
the date) is in the way you lose this important label - you simply
cannot control it.

Therefore, I propose to control label positioning by yourself. This is
what the UpdateAxisLabels method is for (former CreateAxisLabels). It
adds only those labels to the xAxisChartSource which you want to see.
To take care of overlapping labels it contains now a local function
"CalculateDelta" which estimates the label size and its positioning
and adjusts the label interval "delta" such that overlaps are avoided.
It is not yet perfect, maybe you can improve it by yourself and post
the result here. I am not quite happy with this method because it does
what TDateTimeIntervalChartSource should do, but this is somehow
screwed up by the omitted data ranges.

UpdateAxisLabels is called whenever something relevant to the labels
occurs, i.e. after form resizing or chart zooming.

Moveover, the demo contains quite complete handling of zooming/panning
by means of mouse drags and mouse wheel. There is also a zoom history
which allows you to go back to the previous zooming state. See the
instructions at the top of the main form.

And I also used the TChartNavScrollbar as a tool for quick navigation
through a large dataset.

----------------------------------------------------------------------
wp · 2015-02-13 16:15

Another version of the demo which more clearly shows the individual
days by means of a daily stripe pattern:
Add another horizontal axisAt first make it a "top" axis to
distinguish it from the bottom axis, at the end you can make it a
bottom axis as well.Do NOT assign a transformation to it. The new axis
is automatically linked to the bottom axis and uses the transformed
values this way.In the "Intervals" of this new axis, disable all
options except for aipUseNiceSteps. Set Intervals.NiceSteps to 0.1
only to get labels at 0, 1, 2, etc - these are the full days of the
transformed bottom axis.When you run there should be only integer top
labels only, and they should coincide with the 9:00 labels of the
bottom axis.In order to create the stripe pattern, add a TAChartStyles
component.Assign this component to Marks.Stripes of the top axis.Click
the "..." button next to Styles in the Object Inspector. Add two
Styles. They will be switched from day to day.For each style, set
UsePen and UseFont to falseSet Brush.Color of the first style to some
bright color (clSkyBlue) and Brush.Color of the other style to some
other color (clMoneyGreen)Turn off the axis labels by Marks.Style =
smsNoneMake the top axis a second bottom axis (Alignment = calBottom)

----------------------------------------------------------------------
frederic · 2015-02-16 11:52

Wp

very impressive results wp.

I looked into the calculatedelta function, which should rule the
distance between the date time labels .By the introduction of a second
bottom axis the problem of overlapping only occur by time labels of
neighbouring days and  only when the distance of  the marks position
of last time label of the day to the marks position of of the starting
time on the next day, is smaller then  half the time label width . 
However I could not find the solution yet.

frederic

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frederic · 2015-02-17 09:00

update:

there is a dependency with the position of opening time and closing
time and the number of opening hours.

The datetime_intervals - array should match with the number of opening
hours:
When we have a starting time at 0:01 at night and closing 1 minute
before midnight then  there is absolute no overlapping.
Having an opening at 9:00 h and closing at 11:00 h  then there is a
permanent overlap of labels at 9:00h

for my specific case I could live with the result up till now but For
a more generic solution will I am going to look into this direction

frederic

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frederic · 2015-02-17 11:19

it looks like the problem is solved

i changed the datetime_array to the following:

Code: [Select]DATETIME_INTERVALS: array[0..7] of TTime = (
      1*ONE_MINUTE, 5*ONE_MINUTE,
      15*ONE_MINUTE,
      ONE_HOUR,  4*ONE_HOUR,
      1.0, 5.0, 25.0);    
The idea is that there is sufficient space for the new labels whilst
zooming and unzooming .
The ratio between the intervals should therefore be larger dan a
factor 3-4 to get consistent results

frederic

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wp · 2015-02-17 18:35

QuoteThe ratio between the intervals should therefore be larger dan a
factor 3-4 to get consistent resultsNot sure what you mean here. But
the label overlap in my example in which the first label is at 9:00
and the last label at 19:00 happens because the label distance is
calculated for the first two labels of a day, but the last one can get
much closer to the first one of the next day depending on label
interval. You can avoid this overlap if you extract from my code a
function "LabelsOverlap(ATime1, ATime2): Boolean" which checks the
widths of these two adjacent tables and compares them with their
distance on the axis. If the last label of a day overlaps with the
first label of the next day you can just delete the last label of the
day from the chartsource
(xAxisChartSource.Delete(xAxisChartSource.Count-1)). This results in a
non-linear spacing of the labels, but this looks definitely better
than overlapping labels.

----------------------------------------------------------------------
frederic · 2015-02-18 09:25

wp

or always skip the last time label of any day in UpdateAxislabels:

Code: [Select]if DELTA < 1.0 then  begin
   if dt > trunc(dt) + EndTime then begin
            // skip always last time label of a day<------
       xAxisChartSource.Delete(xAxisChartSource.Count-1) ;
        dt := trunc(dt) + 1 + StartTime;
        if trunc(dt) = EndDate then break;
        format := TIME_FORMAT + LineEnding + DATE_FORMAT;
        end;
  end; 
this is the most simple approach.

what not have been solved is the the handling of free
days(christmas,new year etc).
I intend to make a list of dates free days per year  and test the
dates in UpdateAxislabels

Code: [Select]  // Skip weekends
            weekday := DayOfWeek(dt);
            if ((weekday in [1, 7] )  or freeday) then
               begin
                 dt := dt + 1;
                 Continue;
               end;          

frederic

----------------------------------------------------------------------
wp · 2015-02-18 09:53

QuoteI intend to make a list of dates free days per year  and test the
dates in UpdateAxislabelsYes - that's exactly how I would do it. But
make sure that the free days are handled in the transformation
procedures as well (AddWorkday, CountWorkdays), otherwise axislabels
and x values will get out of sync (To check this issue assign the true
date to each data point and turn on the series labels as I did in the
first sample).

----------------------------------------------------------------------
frederic · 2015-02-21 14:50

wp
By introducing the above method in my application it was very soon
clear that this method will unfortunately not be applicable in my
situation.
The preveous testing was done with a random function , but also a
random function in the x-axis.
In order to simulate where I was looking for ,I made a sine-function
based  on 1- minute data instead of this random x -function and got
the attached picture.

Then i realised that i have data  available on 1 minute basis during
the  times that shops are open. These data are listed together in one
big file so that the last minute of a day at closing time will be
directly followed by the first  minute after starttime of the next
working day. The line numbering of this file is,in fact ,the linear
scale of the bottom axis.Because all the calculations and results are
based on this line numbering so do all the derived calculations.The
showing of the datetime labeling is only for presentation reasons and
will be useful when grafical projections from history into the future
days are being made but everything is based on the lineair
linenumbering.
Therefore the x-axis should be based on a linear scale( the 1 minute(
or X- minute or x-days) numbering and  X-axis labeling with datetime
indication should  be derived from that  .
The only restriction is that datetime labels do not overlap .So no
ChartAxisTransformations for the X-axis in this case.

At the moment I have solved this by making use of vertical
constantlines in order to indicate the separation of the day and hours
and using a crosshair with datetime indication and value of the data
per minute .There is bottomaxis labeling but that suffered from the
label overlap and therefoore made invisible.

It could be of help when the vertical constantline would have a label
markation at the bottomaxis which you could fill with date or a time
markation; but that is not foreseen in its properties.
So all X-axis info has to ome from the crosshair

The futher disadvantage is that the croshair is only showing datetime
info when there is XY info is available .

frederic

----------------------------------------------------------------------
wp · 2015-02-21 18:18

I don't see the problems. In my code above, the data are generated in
"CreateData" at random intervals. If you have equally spaced data
points in minutes then you can calculate the date/time for each data
point from the data point index and the start date and shop-opening-
time. Of course you have to apply the transformation to get "true"
datetimes. Something like this:

Code: [Select]const
  MINUTES_PER_DAY = 24*60;

{ Converts the line number which represents the number of minutes
passed since
  the first line in the file, to the date/time value of this entry. It
is
  assumed that the first line corresponds the the date "StartDate" and
the
  time "ShopOpensAt".}
function TForm1.ConvertLineNumberToDateTime(ALineNumber: Integer):
TDateTime;
var
  MinutesWhileShopIsOpen: Integer;
  days: Integer;
  minuteOfDay: Integer;
begin
  MinutesWhileShopIsOpen := trunc((ShopClosesAt - ShopOpensAt) *
MINUTES_PER_DAY);
  days := ALineNumber div MinutesWhileShopIsOpen;
  minuteOfDay := ALineNumber mod MinutesWhileShopIsOpen;
  Result := AddWorkdays(StartDate, days) + minuteOfDay/MINUTES_PER_DAY
+ ShopOpensAt;
  // AddWorkdays is in the code provided in a few posts above
  // ShopOpensAt and ShowClosesAt were formerly named StartTime and
EndTime, respectively.
end;

procedure TForm1.CreateData;
const
  NUM_LINES = 50000;
  EPSILON = 1.0/(24*60*60);  // 1 second accuracy when comparing time
values
var
  i: Integer;
  dt: TDateTime;
  y: Double;
  s: String;
  line: Integer;
  MinutesWhileShopIsOpen: Integer;
begin
  StartDate := EncodeDate(2014, 1, 1);  // The first line in the file
corresponds to this date
  ShopOpensAt := EncodeTime(9, 0, 0, 0);  // Shop opens at this time
  ShopClosesAt := EncodeTime(18, 30, 0, 0);  // Shop closes at this
time
  MinutesWhileShopIsOpen := trunc((ShopClosesAt - ShopOpensAt) *
MINUTES_PER_DAY);

  for line:=0 to NUM_LINES-1 do begin      // each line in the file
advances the time by 1 minute
    dt := ConvertLineNumberToDateTime(line);    // Converts line index
to a "true" date/time
    s := FormatDateTime('dd/mm/yy hh:nn', dt);  // Store the
calculated date/time to check correctness, can be omitted if this is
ok

    // Which data do we plot against this date/time?
    // I am selecting the number of minutes passed while the shop is
open
    y := line mod MinutesWhileShopIsOpen;
    Chart1LineSeries1.AddXY(dt, y, s);

    // if the current line corresponds to the last minute of a day
then it is a good idea
    // to add a break to the line series to avoid a connecting line
from this
    // last day value to the first value of the next day.
    if SameValue(frac(dt), ShopClosesAt-ONE_MINUTE, EPSILON) then   //
requires unit "Math"
      Chart1LineSeries1.AddXY(dt, NaN);
  end;
  Chart1.Prepare; 

  // This is the date of the last data point. Needed for the
transformations.
  EndDate := trunc(dt);
end;

----------------------------------------------------------------------
wp · 2015-02-21 20:39

Here is another version of the demo. It plots 50.000 data points in
1-minute intervals. It uses two x axes, each with its own ChartSource
to provide the labels, a time and a date chartsource. The time labels
adjust themselves such that overlapping is completely avoided -
hopefully... (the last day label is removed if it overlaps with the
first label of the next day). The date labels are in increments of 1
and are linked to the ChartStyles to provide a striped background per
day. If you zoom out a lot the time labels are suppressed, and the
date labels switch to weekly or monthly intervals. Weekly labels begin
at Monday, monthly labels at the first workday of the month. Pretty
universal... (There is one thing which I do not like: it is possible
to scroll out of the data range using the NavScrollbar or the
MouseWheel - I think I have to dig into TAChart to fix this...)

Unlike my previous posts, I removed the axis transformation component
now because it is easier to synchronize both axes this way. Of course,
some kind of transformation is still needed to close the data gaps
during night and weekend. This is done by the function
ConvertDateTimeToDaysPassed when the data are inserted into the
series.

My sample data just plot the number of minutes passed since the first
minute of each day. You can easily plug in your file data here - it is
in the CreateData method.

The minute counter (line counter in your file) is converted to "days
passed" by means of ConvertLineNumberToDaysPassed. The integer part of
these numbers is the count of full workdays since the first data
point. The fractional part is the fraction of the time of the shop
open hours, i.e. x.0 is at the shop opening hours, and x.99999 is
immediately before the shop closes.

Please study the code, I inserted a lot of comments. You must
understand the principle of the transformation. And you must be
familiar with basic date/time functions provided by fpc. Look at the
unit DateUtils, I used several of its routines.

----------------------------------------------------------------------
frederic · 2015-02-23 11:14

Thanks wp,

it looks like your latest update will overcome the problems i observed
when i tried to use your code.

Indeed i have to learn a lot more about tachart and  do ,in the mean
time, a lot of testing to get more famiiar with it. And it is real
great work  to see  what is possible with Tachart. Great respect for
its developers!!


So i was trying to make a crosshair for your latest code .The
construction itself is not the problem but i wanted to display the
values of the chartsseries in  a statusbar Up till now i used the
vertical constantline X position in a chart.mouse move event as input.
By using that the X position is an integer only showing days numbers ;
so not of great help when you want to show time as well.

The crosshairtool offers me x,y values of the chart.canvas ,but i was
not able  to display the crosshair now.

So how can i use the crosshair tool in this case; is there something
like chart-to-canvas-operation and reverse and how to deal then when
there are no series data available at the canvas minimum or maximum
values of the x-axis ?


frederic

----------------------------------------------------------------------
wp · 2015-02-23 14:42

There is no need to invent a crosshair tool by yourself, it is already
built into the ChartTools.

Double-click on the ChartTools component which is already on the form
and add a DatapointCrosshairTool. If you run the program you will
automatically see the crosshair tool whenever the mouse come close to
a data point. If you want to modify its default behaviour you can play
with its properties:
DistanceMode: if you select cdmOnlyX the cursor will appear whenever
the mouse is close to the x value of a data point, y is ignored.
Similarly with cdmOnlyY.Shape: defines the shape of the cursor,
ccsVertical, e.g. draws only a vertical line instead crossed
horizontal and vertical linesSize: defines the size of the cursor: -1
mean that the cursor runs across the entire chart, otherwise it
defines the length of the lines in pixels.CrosshairPen: determines the
line color, line style etc of the cursor. Note that these become
effective only if DrawingMode is tdmNormal.Shift: defines the mouse or
key event which must occur for the cursor to show. If the set is empty
as by default then the cursor shows up whenever the mouse is near a
data point. If you add, e.g. ssShift, then the SHIFT key must be
pressed additionally.etc.In order to show the current position of the
crosshair cursor in the statusbar you hook into the OnDraw event.
Maybe named a bit misleading for this purpose, this event has
everything ready to get the position of the cursor. The event itself
is not very verbose, but the tool's properties tell you everything.
However the tool parameter passed to the event handler has to be cast
to a TDatapointCrosshairTool to get access to all properties that you
need:
TDatapointCrosshairTool(Sender).Series is the series at which the
crosshair cursor is grabbed (or nil, if the mouse is too far off from
a series). A type-cast to TLineSeries is needed to get access to all
properties of the series.TDataPointCrosshairTool(Sender).PointIndex is
the index of the datapoint grabbed by the cursor.Since in the
CreateData method data were added to the series by AddXY the data are
stored in the internal ListSource of the series. Therefore you can
read the x and y coordinate of the cursor location by looking up the
data point in the series' ListSource. The items stored in the
ListSource are pointers to TChartDataItem records which contain the x
and y coordinates in the corresponding fields. Don't forget to
derefence the pointer:Code: [Select] series :=
TLineSeries(TDatapointCrosshairTool(Sender).Series);   
// of course you can also use Chart1LineSeries1 since your chart
contains only 1 series... 
index := TDatapointCrosshairTool(Sender).PointIndex; 
x := series.ListSource[index]^.X; 
y := series.ListSource[index]^.Y; From the retrieved x and y
coordinates you can construct the string for the statusline. But be
aware that x does not yet lead to a decent date/time string: Data were
added as "days since first data point", therefore you have to
calculate the date from this by inverting the
ConvertDateToTimDaysPassed function.In the attachment you find working
modification of the previous demo, now with datapoint crosshair tool.
The tool is activated by pressing the SHIFT key.

If you want to learn more about TAChart you should have a look at its
documentation
(http://wiki.lazarus.freepascal.org/TAChart_documentation) and the
many tutorials
(http://wiki.lazarus.freepascal.org/TAChart#Documentation). I am
intending to write another tutorial, covering the subject of this
discussion.

BTW: What is the quantity which is measured regularly in 1-minute
intervals and which you are plotting?

----------------------------------------------------------------------
frederic · 2015-02-23 16:12

thanks again wp

QuoteWhat is the quantity which is measured regularly in 1-minute
intervals .................?
i can control the amount minutes of course  but roughly 10000
minutes,but i was just about of studying if summarizing in 30 or 60
minutes would be more appropiate when i want to cover a wider time
frame

Quote...................and which you are plotting..
what do you mean here ?
when you are referring to DATETIME_INTERVALS

I used  following array
 DATETIME_INTERVALS: array[0..7] of TTime = (
      1*ONE_MINUTE,  5*ONE_MINUTE,
      15*ONE_MINUTE,
      ONE_HOUR, 2*ONE_HOUR,
      1.0, 7.0, 30.0);  

update 24febr: in the mean time i find out that this setup has effect
on the display of the data labels in some stage of zooming ; they
fully disappear whilst this is not the case in your datetime_interval
array ...... so this needs some further study.


one question for the crosshairtool:

I saw that the datetime presentatin stops when the series value stop.
is it possible to show also datetimes while the Y-value of the series 
=nil

frederic

----------------------------------------------------------------------
frederic · 2015-02-25 09:43

wp

my question about the x-axis range of the crosshair can be solved very
easy.

In the data presentation there a few horizontal lines which can serve
as the reference chart line. I can modify the max range by setting the
range wider than the  available time range of the measured and
calculated data points.

You can extend this a little further and prepare x-axis definition for
a full year or even make it a standard option for a customized
datetime axis in tachart in the future where you can set
opening/closingimes and free day in a year via properties.

again thanks for your assist here

frederic

----------------------------------------------------------------------
wp · 2015-02-25 10:03

Sorry I did not see your edit yesterday.

Quote from: frederic in the mean time i find out that this setup has
effect on the display of the data labels in some stage of zooming ;
they fully disappear whilst this is not the case in your
datetime_interval arrayWhen exactly does this occur? Since the
smallest interval used in the label finding procedure is 1 minute,
labels will eventually disappear when you zoom in so strongly that the
1-minute interval is wider than the width of the chart. Of course, you
can add intervals of 30 sec, 15 sec, 10 sec, 5 sec, 2 sec, 1 sec,
etc., to the method. But since you mentioned a 1-minute interval of
the data, I did not see this to be necessary.

Quote from: fredericI saw that the datetime presentatin stops when the
series value stop.
is it possible to show also datetimes while the Y-value of the series 
=nil If you mean that there are no labels beyond the range of the data
- well, that's the way it is designed. Labels appear only if they have
been added in the UpdateLabels method. So, if you need more labels,
add more of them in this procedure. The axis chartsource method gives
you full control over the labelling process.

Quote from: fredericQuote from: wp...................and which you are
plotting.. what do you mean here ?I mean: which kind of data is on the
y axis? I a looking for a good example fot the tutorial. For a shop, I
could imagine: Price of an article sold logged when the cashier
closes, or number of customers in the shop.

----------------------------------------------------------------------
frederic · 2015-02-25 13:06

wp

it all about keynumbers and financial ratios in inventory movements
,not very exiting  for a tutorial.

for the presentation i looked at graphs presented at yahoo for
stockmarket .There you have same problematic and people are more used
to it.

frederic

----------------------------------------------------------------------
wp · 2015-02-25 14:35

How can I get stock data per minute or hour from yahoo? I only know
this url where the closest interval is 1 day (although this would be
enough to show how to skip the weekends in the chart...)

Code: [Select]const
  URL_MASK = 'http://ichart.yahoo.com/table.csv?s=%s&a=%d&b=%d&c=%d&d=
%d&e=%d&f=%d&g=%s&ignore=.csv';
  // s: stock
  // a: start month (-1), b = start day, c = start year
  // d: end month (-1), e: end day, f: end year
  // g: interval ("w" = week, "d" = day)

----------------------------------------------------------------------
frederic · 2015-02-25 14:55

wp
QuoteWhen exactly does this occur?
transition from date to introduction of time labels see attachment

I tried several datetime intervals, yours appeared oke ; the others
not.

other frames with smaller frames are not needed.

frederic

----------------------------------------------------------------------
frederic · 2015-02-25 15:54

wp

I thought i  did download minute data from yahoo in the past ,but it
looks that is not possible anymore?

I did some testing with 1 minute files of eurostoxx50 in the past and
have some 1 minute files  around november 2013 ;however per day , so
you have to glue them together to get your demonstration effect

it covers more than amonth

these are csv files are in .prn format

but there is certainly more available on the internet

frederic

----------------------------------------------------------------------
wp · 2015-02-25 21:37

Quote from: frederictransition from date to introduction of time
labels see attachment
I tried several datetime intervals, yours appeared oke ; the others
not.
other frames with smaller frames are not needed.
My code was intended to demonstrate the principle only, but not to
cover all cases. When you change the DATETIME_INTERVALS array you must
also adapt the index from which the DayChartSource begins to search.
This is because both TimeChartSource and DateChartSource use the same
procedure for calculating the labels. But for the DateChartSource it
does not make sense to begin with the minute-intervals. Therefore, the
local procedure "CalculateDelta" defines the starting index i for the
best interval for both chartsources separately - both cases are
distinguished by the format string passed as a parameter. Look for the
line

Code: [Select]i := IfThen(AFormat = DATE_FORMAT, 12, 0);

In my selection of intervals, index 12 points to the 1-day interval.
If you drop some intervals you have to replace this value by the index
of the array element 1.0 (1 day). Or, to be more general, add a simple
function which looks for the 1.0 in the array.

Thanks for the hint on the stock data. I found this reference
(http://www.quantshare.com/sa-426-6-ways-to-download-free-intraday-
and-tick-data-for-the-us-stock-market) which seems to provide 1-minute
data, but did not yet check it out.

----------------------------------------------------------------------
frederic · 2015-02-26 09:04

wp

I understand it.

interesting link by the way .
 Very often howver you have to pay for using  the software for
downloading the free data. It is not clear if that is the case here

frederic

----------------------------------------------------------------------
frederic · 2015-03-09 20:14

wp

in the meantime i got hold of eurostoxx50 1 minute data between
31-10-2013 and 10-12-2014; so more than a year

these are data already checked on gaps and the file i can deliver
has the line format :

linenumber;datetime;doubledatetime;close;stoch1;stoch2;


these files are big:
25 days in 7z  equals 251 kb ;12700 lines

ps stoch1 and stoch2 stands for a stochastic oscillator (2 different
settings) which are often showed together with index chart  in a pane
setup.

if you are interested in these data for your tutorial give me a sign

frederic

----------------------------------------------------------------------
wp · 2015-03-09 21:24

Is it possible to download these files somewhere? I must present the
readers of the tutorial a way how to get the data. And of course, it
must be a free download.

----------------------------------------------------------------------
frederic · 2015-03-10 11:07

wp,

i see. These data are ,in this form ,not freely available .
They originate from someone who collects  intradaydata realtime from
multiple sources on the internet and builds files for his private use.

I needed these files also  for testing whilst I was adapting  your
code in my application.

as i mentioned before I wanted to use multiple panes  there but i ran
into an error which i could not solve and got back to your project and
adapted it to read a file and i was able to reproduce the error

I followed the instructions in the panes tutorial and before the
introduction of the axistransformations it was succesfull !!   see the
printscreen in the attachment ( btw group=2 for all 3 axis,group=1 for
bottom2

then i filled in de marks.range and the axis range of all 3 left
axises and made the usemin and usemax true and put the 3
axistransformations on the chart ; set the min/max to respectively
0-1,1-2,2-10. and connected the 3 left axises to axistransformations

compiling was oke; but during debugging the SIGSEGV error came up:

in   tatransformations.pas line 672:
Code: [Select]procedure TAutoScaleAxisTransform.ClearBounds;
begin
  inherited ClearBounds;
  with TAutoScaleTransformData(FDrawData) do begin
    FMin := SafeInfinity;         
<<----------------------------------------- error
    FMax := NegInfinity;
    FOffset := 0.0;
    FScale := 1.0;
  end;
end;     
what could this be ?

frederic

----------------------------------------------------------------------
wp · 2015-03-10 17:02

Yes, I saw the same issue when I was introducing panes in my demo
(which you'll find as attachment). The debugger showed me that the
SIGSEGV occured in the PrepareAxis method called immediately from
FormCreate. The problem here is that the chart has not yet been drawn
and therefore the axis limits are not yet known. But you can enforce
this calculation by adding a Chart1.Prepare to the start of
PrepareAxis.

In my demo you see two series arranged in two panes. The first pane
ranges between 0 and 2, the second one between 4 and 6. These numbers
are specified in the Range of the AutoscaleAxisTransform and mean that
the internal y axis runs between 0 and 6, the lower third (0..2) is
covered by the first series, the medium third (2-4) is empty, and the
upper third (4-6) is occupied by the other series.

If you want to restrict axis labels to the part of the corresponding
series set the axis Marks.AtDataOnly to true. And set the title's
PositionOnMarks to roughly center the axis title with respect to the
corresponding series data (but centering is not very good, though...).

There is also a zero-line for the upper series (a
TConstantLineSeries). I did not assign an axis to it therefore you
have to set its Position to 4 (that's the internal axis value where
the upper pane starts) - just to confuse you   ...

Play with this demo, modify properties, see what happens and try to
understand why.

----------------------------------------------------------------------
frederic · 2015-03-11 09:14

wp ,

of course  , i understand now.

you introduced the constantline as separation line between the panes .
that is a good idea to provide clarity between the panes .

btw I saw that the crosshair tool needs a maximum Xaxis limitation  in
order to avoid a SIGSEGV error

thanks

frederic

----------------------------------------------------------------------
frederic · 2015-03-17 15:19

wp

Two questions


i see that some where i introduced  a mistake . In the attachment of
the printscreen you see that the date indication and the stripes are
not at the right place. I cannot find the cause for it.

studying your code i spotted a line in the calculation of the delta
which i don't understand . please explain

Code: [Select]
...........
 while DateOf(dt) <= EndDate do begin
      // Skip weekends
      weekday := DayOfWeek(dt);
      //here will come a statement needed for check of extra free days
      if weekday in [wdSunday, wdSaturday] then begin
        dt := dt + 1;
        Continue;
      end;


      // Add date+time to axis chartsource formatted according to
"format"
      days := ConvertDateTimeToDaysPassed(dt);
      s := IfThen(NoLabels, '', FormatDateTime(format, dt));
      AChartSource.Add(days, days, s);//   <<--   what is happening
here PLEASE EXPLAIN
      // next label
      prev_dt := dt;
      if DELTA < 30 then begin
        dt := dt + DELTA;
        if DELTA < 1.0 then begin
          if dt > DateOf(dt) + ShopClosesAt then begin
            dt := DateOf(dt) + 1 + ShopOpensAt;
            // Remove the last label of a day if it overlaps with the
first label
            // of the next day
            if LabelsOverlap(prev_dt, dt, format) then
              AChartSource.Item[AChartSource.Count-1]^.Text := '';
          end;
        end;

----------------------------------------------------------------------
wp · 2015-03-17 16:36

Unfortunately you do not show all your code.

The stripes are offset because they seem to have a different starting
point. You must make sure that the datasources of both axes start at
the same time. Maybe the first datapoint of one chartsource starts at,
say, 9:00 and the other source starts at midnight. If both series go
through the axis transformation then the 9:00 data point becomes 0
while the midnight data point becomes some negative fraction. Be
caseful to apply the transformation correctly. To be more precise: I'd
speculate that the first datapoint of the 9:00 series is "startdate +
startime" (where starttime corresponds to 9:00), but the midnight data
start at "startdate" only.

The "AChartSource.Add(days, days, s)" adds the number of days passed
since the 1st data point ("days") as an x and y value to the chart
source, along with the label "s". Using the days also for the y value,
is not necessary, therefore, you can use "AChartSource.Add(days, 0,
s)" (with 0 or any other value for y) as well. But maybe you want to
rotate the chart (interchange x and y) sometimes in the future, hence
I am inserting the value for y as well, and it does not cost anything.
- It has nothing to do with the offset in time scales.

----------------------------------------------------------------------
frederic · 2015-03-17 20:16

wp

QuoteTo be more precise: I'd speculate that the first datapoint of the
9:00 series is "startdate + startime" (where starttime corresponds to
9:00), but the midnight data start at "startdate" only.

your analysis was completely right!
 startdate always starts at 0:00 hours for both bottomaxises.

i did set the datetime of the first line of the file (starting at 9:01
hours) to be equal with startdate; and that is wrong.
so solved.

The second question: I now see that the y-value "days" was an
arbritrary value;
oke ,that solved it!!


thanks again

frederic