UseMin,UseMax,Min,Max behaviour [SOLVED]
lazarus / 55-TAChart

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mtanner · 2015-10-22 12:59

I' drawing a straightforward chart with several TLineSeries. I want
the user to be able, optionally, to control the range of each axis
that is displayed, by means of some input fields next to the chart.
The obvious way to do this is with UseMin, Min etc.  But I don't get
the behaviour I expect. I can extend the range displayed above or
below the range of the points in the TLineSeries, but I cannot set the
range so that some points are excluded. Basically TAGraph seems to
insist of making all the points visible.

Is there some magic option I need to set to get complete freedom in
controlling the range?

I am working on Windows XP with Lazarus 1.4.0.

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christian1987 · 2015-10-22 14:20

Canvas.CopyRect for the axis.

Then

Make your chart huge.

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mtanner · 2015-10-22 14:47

Thanks for your help, but I don't understand what you are trying to
tell me. Could you elaborate a bit please? A quick google of
Canvas.CopyRect doesn't seem to make much sense in the context of my
question.

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wp · 2015-10-22 14:55

No no - no need to play with the canvas!

The chart has a property Extent in which you can preset the axislimits
(Chart1.Extent.YMin := 10, etc) and activate them
(Chart1.Extent.UseYMin := true).

Note that sequential setting of the min/max values may cause trouble
if, for example, the new min is higher than the old maximum. It is
better to use the combined call "FixTo" like here:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses 
TAChartUtils, TATypes;var  extent: TDoubleRect;  ...  extent :=
Chart1.GetFullExtent;   // get current range of x and y axis 
extent.a.y := 10;  extent.b.y := 100;   // y axis will range between
10 and 100 now  Chart1.Extent.FixTo(extent);

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mtanner · 2015-10-22 18:29

Thanks WP, that works ok, and is tidy to code.

I'm doing my first serious project in Lazarus, having extensive
experience with Delphi (D6) and TeeChart. Some things are a bit
different!

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mtanner · 2015-10-22 18:30

I'm also new to this forum. How do I mark a question closed or solved?

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wp · 2015-10-22 18:44

Edit the first post and add a "[SOLVED]" to the title.

Have fun with Lazarus!

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wp · 2015-10-22 18:50

Quotehaving extensive experience with Delphi (D6) and TeeChartI once
wrote a (still incomplete) comparison of TeeChart and TAChart. And
maybe you should also know that there is a large doc file and a series
of tutorials.