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My question is based on the discussion that I started: Plot, extract data to a file

The method proposed works well for the Plot command, but what about LogLinearPlot? This was the original motivation when I started the thread. I wanted to extract the data for LogLinearPlot, because I wanted a tighter grid for r $\approx$ 0. Otherwise, I could have just used Table and wouldn't have started the thread. This doesn't work with Table, which produces a uniform grid.

Anyways, this is my code:

LogLinearPlot[{f[r]*r, 0}, {r, 0.0001, 1000}, PlotRange -> {-0.5, 0.2}, MaxRecursion -> 15]
data = Cases[%, Line[data_] :> data, -4, 1][[1]];
Export["~/Desktop/1.dat", SetAccuracy[%, 10], Alignment -> Center]

The catch is that it produces a relative positions of the points on the r axis for the 1st column (r coordinates of the points they would have if the r-axis wasn't set to be logarithmic on the plot).

For example,

-9.210340043    -0.044128619
-9.210320733    -0.04412862

whereas I was expecting something like this:

 0.000110000    -0.044128619
 0.000170000    -0.04412862

The origin of the "fictitious" and real axes coincide. How do I get the actual values of r?

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Your attempt to use the Plot[] mesh, although achievable, doesn't seem justified. You could design your own "meshing" algorithm, fitted specifically to your problem. – belisarius has settled Feb 22 '13 at 2:33
I posted an answer showing how to adapt both of the methods I previously gave. In the future consider mentioning your actual use in questions as that will help answers to be better on target. – Mr.Wizard Feb 22 '13 at 2:41
thanks for help! – molkee Feb 22 '13 at 3:04

1 Answer 1

up vote 1 down vote accepted

You just need to to invert the Log operation that is done on the $x$ data, with Exp:

gr = LogLinearPlot[Sin[x], {x, 1, 10}]

data = Cases[gr[[1]], Line[data_] :> data, -4][[1]];

data = {Exp@#, #2} & @@@ data;


Mathematica graphics

Mathematica graphics

Alternatively you could use the other method, which may be simpler in this case:

{gr, {data}} =
   LogLinearPlot[Sin[x], {x, 1, 10}, EvaluationMonitor :> Sow[{x, Sin@x}]]



Mathematica graphics

Mathematica graphics

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