TAChart different axes of left and right for different data series
lazarus / 55-TAChart

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grzegorz · 2010-04-09 07:07

Hi all  I'm a beginner Lazarus user and i have question:
Is it possible to do different axes left (temperature) and right
(pressure) for different data series on the same graph (common
horizontal time axis)?

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Leledumbo · 2010-04-09 07:27

If you use the snapshot version: yes
Use DataSource property of each axis whose value you want to change

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grzegorz · 2010-04-09 08:08

Quote from: Leledumbo on April 09, 2010, 09:27:36 amIf you use the
snapshot version: yes
QuoteUse DataSource property of each axis whose value you want to
change
but
unfortunately, I do not know how to do it.
It seems too complicated for me.
intuitively tried by a combination of AxisIndexy(tlineseries
properties) with the corresponding axis  same way as in Delphi
(lineSeries.VertAxis: = aRightAxis) but unfortunately does not work

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Ask · 2010-04-09 09:34

You may be interested in tachart/demo/axis/axisdemo project,
"Linear transform" page.

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grzegorz · 2010-04-09 10:15

Quote from: Ask on April 09, 2010, 11:34:05 amYou may be interested in
tachart/demo/axis/axisdemo project,
"Linear transform" page.
in that example, all the vertical axes have the same minima maxima and
scale.
I need to be independent  (pressure, temperature), conected only by
vertical axis (time).

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Ask · 2010-04-09 23:01

Stragne. This example is specifically about representing two series
with different scales
(temperature in degrees Celsius an Fahrenheit, but of course you are
not limited to that).

BTW, please update you Lazarus to latest svn -- I have found a bug in
the example a few days ago.

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grzegorz · 2010-04-10 13:33

Quote from: Ask on April 10, 2010, 01:01:39 amStragne. This example is
specifically about representing two series with different scales
(temperature in degrees Celsius an Fahrenheit, but of course you are
not limited to that).

BTW, please update you Lazarus to latest svn -- I have found a bug in
the example a few days ago.
in that example, the axis of the left and right are not independent.
The relationship between the axes describes ChartAxisTransformations.
thanks
sorry for my bad english

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Ask · 2010-04-11 07:52

You are right, automatic transformation are is on my TODO list.
For now, you may manually set linear transformation parameters.

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ThB · 2010-12-31 10:29

Automatic axis scaling of LineSeries2 (on right axis) depending on
LineSeries1 (left axis) can be done this way:

Code: [Select]var tmp: Double;
...
If Chart1LineSeries1.Active then
  tmp := Chart1LineSeries1.GetYMax - Chart1LineSeries1.GetYMin
else
  tmp := 1;

If (Chart1LineSeries2.GetYMax <> Chart1LineSeries2.GetYMin) AND
   (Chart1LineSeries2.IsEmpty = false)
then begin
  LAT1.Scale := tmp / (Chart1LineSeries2.GetYMax -
Chart1LineSeries2.GetYMin);
  LAT1.Offset := Chart1LineSeries1.GetYMin - LAT1.Scale *
Chart1LineSeries2.GetYMin;
end;

I use it in my own project.

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Ask · 2011-01-05 16:04

In recent versions, you can also use TAutoScaleAxisTransform
(see "Auto scale" checkbox in the axisdemo).