How to Use Labeled BottomAxis
lazarus / 55-TAChart

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Manda · 2010-09-26 16:49

Hi,

I'm new to Lazarus. Using Win32/0.9.28.3/SVN 27462/FPC 2.4.0.

I have a memo with a SQL statement and a button. When I click the
button, the first column should be my X Axis, and the other columns
should be all in the Y Axis.

For each query.fields.count I create a new BarSeries. Except for the X
(1st column).

While not query.eof, I addXY for such serie.

When X is string: FBar.AddXY(SEQ, Y, X, Color); //SEQ is a count 1, 2,
3, ..., N
When X is double: FBar.AddXY(X, Y, '', Color);

Issue 1: I can't stack my bars. They appear all overlaied when I have
multiple Y (Y1, Y2, Y3). Multibar is unavailable. I tried to use Width
property for each bar, but I didn't figured out how to desloc 2nd,
3rd, ... by the same width.

Issue 2: I can't change BottomAxis marks to legend of the XY point.
BottomAxis.Marks is unavailable. Didn't found how to use the
BottomAxis.MarkToText function.
FBar.Marks.Style := smsLegend show all legend under the bar, not in
the X Axis.
Using Char1AxisList1MarkToText I can change X Axis texts but I didn't
found how to recover all X labels from my TBarSeries.

I read and tried all tachart demos. But couldn't solve the 2 problems
above. Could someone give a hint?

Thanks in advance.

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Manda · 2010-09-26 19:18

Found a solution for Issue 2.

I created a global TStrings and a global Flag. Before adding my
series, I filled my StringsList with query.column1 (X) values. The
flag tell me the type of X (string or double).

In Chart1AxisList1MarkToText procedure, I put the code:

Code: [Select]    if (gXDouble <> 1) and (sLegenda <> nil) then begin
//X is string [0, 1, ..., N]
      AText := '';
      if (Trunc(AMark) = AMark) and (AMark >= 0) then begin
        if (sLegenda.Count > Trunc(AMark)) then AText :=
sLegenda[Trunc(AMark)];
      end;
    end;

Still looking for a solution for my MultiBar series.

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Ask · 2010-09-28 20:18

Quote from: Manda on September 26, 2010, 06:49:28 pmUsing
Win32/0.9.28.3/SVN 27462/FPC 2.4.0.

This is quite recent SVN. It is probably 0.9.29, not 0.9.28.3

Quote from: Manda on September 26, 2010, 06:49:28 pmFor each
query.fields.count I create a new BarSeries. Except for the X (1st
column).
While not query.eof, I addXY for such serie.
When X is string: FBar.AddXY(SEQ, Y, X, Color); //SEQ is a count 1, 2,
3, ..., N
When X is double: FBar.AddXY(X, Y, '', Color);

I am confused. Do you create a bar series for every record in the
dataset?
How can X be string and double for the same query?
Or do you have several queries at once?
Did you consider using dbchartsource?

Quote from: Manda on September 26, 2010, 06:49:28 pmIssue 1: I can't
stack my bars. They appear all overlaid when I have multiple Y (Y1,
Y2, Y3). Multibar is unavailable. I tried to use Width property for
each bar, but I didn't figured out how to desloc 2nd, 3rd, ... by the
same width.

If you use multi-valued source, the (single) bar series should
automatically display stacked.
See demo/multi/ for an example. If you do not have this demo, then
your version
is not actually SVN trunk, and you should either update or wait for
release.

If you need a clustered instead of stacked bars, then you should lower
bar width
and manually offset series by increasing X value for some of them.
This may be improved -- please create a feature request in the
bugtracker.

Quote from: Manda on September 26, 2010, 06:49:28 pmIssue 2: I can't
change BottomAxis marks to legend of the XY point.
BottomAxis.Marks is unavailable.

This is definitely a problem, but I can neither understand nor
reproduce it.
What do you mean by "unavailable"? The property does not exist at all?
Or it exists but is read-only? Or something else?
Please create and post a test project demonstrating your problem,
preferably to the bugtracker.

Speaking about the OnMarkToText event, it's disadvantage is that,
depending on chart zoom level,  it may be called for any X value,
not only the values corresponding to the chart source points.
So if you want to limit X marks to source points only, you should
use Axis.Marks.Source property -- see demo/axis for an example.

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Manda · 2010-10-02 21:52

Hi Ask, thanks for answering.

Thanks for your barwidthpercent and X offset tip. I have my multibar
working well now.

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Ask · 2010-10-04 10:46

Since r27570, you can use BarOffsetPercent to simplify clustered bar
chart drawing