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I have the following code.

\begin{tikzpicture} 
\begin{axis}[domain = -2:2
         ,y domain = -2:2,view={0}{90}] 

\addplot3[contour gnuplot={number=10},thick,domain=-2:2]
{0.5*exp(-0.2*abs(x)-0.2*abs(y))}; 
\end{axis} 
\end{tikzpicture}

But I'd like it to plot just the area inside a circle x^2+y^2 < 1 Any Idea?

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Why not a simple circle filled? –  percusse Feb 10 '13 at 2:19
    
@percuße I want it to be filled by the mentioned contour. How? –  batista cori Feb 10 '13 at 2:21
    
Do you mean clipping with a circle or a circle under these countours? –  percusse Feb 10 '13 at 2:23
    
@percuße clipping with a circle. –  batista cori Feb 10 '13 at 2:24
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1 Answer

up vote 4 down vote accepted

I can't see where that extra 3.5 scaling factor comes from but this should be robust to scaling and other shifts etc.

Edit : the clipping path can be much simplified thanks to Christian's correction.

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.7}
\begin{document}
\begin{tikzpicture} 
\begin{axis}[domain = -2:2,y domain = -2:2,view={0}{90},grid=both] 
\pgfplotsextra{%
\clip (axis cs:0,0) circle (1 and 1); 
}
\addplot3[contour gnuplot={number=10},thick,domain=-2:2]{0.5*exp(-0.2*abs(x)-0.2*abs(y))}; 
\end{axis} 
\end{tikzpicture}
\end{document}

enter image description here

share|improve this answer
    
worked! Thanks. –  batista cori Feb 10 '13 at 2:59
    
If you omit units after the circle path, the radii will be interpreted as (pgfplots!) axis units: \clip ... circle (1 and 1); . Note furthermore that \pgfplotsextra is the correct choice, but is is inserted automatically if you omit it. –  Christian Feuersänger Feb 10 '13 at 16:15
    
@ChristianFeuersänger Much better and obvious. I didn't know that. Thank you. By the way can you see why the need to scale with 3.5? –  percusse Feb 10 '13 at 16:19
    
This is a consequence of the internal data scalings. Consequently, the 3.5 would have been wrong if the limits where from, say, -200 .. 200. –  Christian Feuersänger Feb 10 '13 at 21:07
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