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LogPlot. Without Log, there is no problem. But when I try to plot with Log

jabir Hakami
Posted 10 years ago

Hi, I having hard time with LogPlot.

Please find the attach file. Without Log, there is no problem. But when I try to plot with Log gives a lot of errors I spen a lot of time to see why!! I really apreciate your help Regards Jabir

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POSTED BY: jabir Hakami
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Erik Mahieu
Erik Mahieu
Posted 10 years ago

But my plot shows AND RE and Im!? Here is a plot of only the imaginary part (this is in fact a rescaled plot of the orange curve above). I do not see the problem...
POSTED BY: Erik Mahieu
jabir Hakami
jabir Hakami
Posted 10 years ago

Thank you very much. But this is did not solve the problem. For examble, if we plot just the imaginary part which gives real numbers , the problems still there. Regards Jabir
POSTED BY: jabir Hakami
jabir Hakami
jabir Hakami
Posted 10 years ago

Thank you very much. But this is did not solve the problem. For examble, if we plot just the imaginary part which gives real numbers , the problems still there. Regards Jabir
POSTED BY: jabir Hakami
Erik Mahieu
Erik Mahieu
Posted 10 years ago

The log of a negative number is an imaginary number. You can change the sign of the real parts that are negative as follows:

Eps1[\[Omega]_] := (p[\[Omega]][[1]]^2 - p[\[Omega]][[2]]^2) + 
   I*2*(p[\[Omega]][[1]]*p[\[Omega]][[2]]);
LogPlot[{-Re[Eps1[\[Omega]]], Im[Eps1[\[Omega]]]}, {\[Omega], 1, 5}, 
 PlotStyle -> Thick, PlotRange -> All]

POSTED BY: Erik Mahieu
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