TAChart: Logarithmic diagrams

[wp]

When plotting data on logarithmic axes the logs have to be calculated explicitly before adding the data to the series. This is quite unusual: Excel, gnuplot etc. accept direct data and calculate the logs themselves. This would make life easier when an applications allows the user to switch between linear and log scales.

I fear that some internal routines might get screwed up, but is it possible to have that behavior in TAChart as well? I mean that the ChartTransformation should be responsible for calculating the logs of the data, not only of the axis labels.

[Ask]

When plotting data on logarithmic axes the logs have to be calculated explicitly before adding the data to the series.

Why do you think so? Please look at axistransf demo -- does it not work for you?

[wp]

Enclosed is a simple project plotting the function y = exp(-x). On a semilog scale the exponential curve must become a straight line - that's simple math. In this program, however, this is true only if the two lines marked by the comment "Needed" are active.

What am I doing wrong?

[Ask]

You did not set AxisIndexY property.
See http://wiki.lazarus.freepascal.org/TAChart_documentation#Axis_transformations

[wp]

Ah! Guess I should read the docs once more...