How to plot logarithnic line chart?
lazarus / 55-TAChart

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Vitala · 2009-11-05 17:15

Hello, all. I desided to use lazarus for my new job. I have been asked
to make program, plotting line charts (calculated by another program,
written on Fortran77). I used TAChart? so i have made it, but
employers said: "Some plots must be logarithmic, make checkbox".
Anybody, please, help me, i tried to edit TAChart unit files, but i
break it and now it doesn't work . If you used logarithmic plots in
Lazarus, tel me, how can i make it?

Sorry for my bad english, i haven't had practise for long time

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Ask · 2009-11-07 05:36

Currently, TAChart does not support logarithmic axis scale directly,
although such support is planned.
You can create a Mantis issue with the feature request,
and hopefully I will address it in a month or two.
Of course, patches are welcome ;-).

Meanwhile, what series type do you use?
If you use TFuncSeries, or standard series with
TUserDefinedChartSource,
then you can simply add Log() call to the event handler.

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Vitala · 2009-11-07 16:35

I use just TChart and TLineSeries, and i fill series by numbers from
array, loaded from txt file. Adding Log() is bad variant, because
there must be result of calculations, but not its logarithm in the
plot.
I didn't understand, what means "Mantis issue with the feature
request" and how to create it.
Can you give me explanations of functions in TChart (better than it is
in .pas files), i will try to "upgrade" this unit.
Yeah, I use version 1.0 with date in redme 01/06/2008. Is there any
newer version?

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Ask · 2009-11-11 11:30

QuoteI use just TChart and TLineSeries, and i fill series by numbers
from array, loaded from txt file.You can try using
TUserDefinedChartSource -- see funcdemo for an example.

QuoteAdding Log() is bad variant, because there must be result of
calculations, but not its logarithm in the plot.
I do not fully understand this sentence. Can you give an example?

Quotewhat means "Mantis issue with the feature request" and how to
create it.
See http://bugs.freepascal.org/

QuoteYeah, I use version 1.0 with date in redmeVersion number in
readme does not mean much.
TAChart is now a part of Lazarus and have the same version as Lazarus
itself.

Last stable Lazarus version is 0.9.28.2.
If you want to use the latest development version, get if from the
Lazarus svn trunk.

QuoteCan you give me explanations of functions in TChartLatest (trunk)
version have built-in help for some of the classes and functions.

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wp · 2014-01-17 11:53

Don't edit TAChart units. If you did delete everything and do a new
install of the current version.

To create a logarithmic plot, see the tutorial http://wiki.lazarus.fre
epascal.org/TAChart_Tutorial:_ListChartSource,_Logarithmic_Axis,_Fitti
ng