# Area between graphs of two functions

This is a follow-up question to Area between curves.

After one day, i found out how to do it in LaTeX (Miktex):

\documentclass[10pt]{article}
\begin{document}
\begin{pspicture}(-3.5,-0.5)(4,7)
\begin{psclip}{
\psplot[linestyle=none,algebraic,plotpoints=2000]{-3}{3}{x^2+1}%
\psline[linestyle=none,algebraic,plotpoints=2000](-1,1)(-1,2)(2,5)(2,1)
}%
\psframe*[linecolor=cyan,fillstyle=solid](-1,1)(2,5)
\end{psclip}
\psplot[algebraic,plotpoints=2000,yMaxValue=5.6]{-2.3}{2.3}{x^2+1}
\psplot[algebraic,plotpoints=2000]{-3.5}{2.5}{x+3}
\psaxes{->}(0,0)(-3.5,-.9)(4,6.5)
\uput[-90](3.9,-.2){$x$}
\uput[-135](-.2,6.7){$y$}
\end{pspicture}
\end{document}


Strange that the followwing code doesn't work:

\documentclass[10pt]{article}
\begin{document}
\begin{pspicture}(-3.5,-0.5)(4,7)
\begin{psclip}{
\psplot[linestyle=none,algebraic,plotpoints=2000]{-1.2}{2.2}{x^2+1}%
\psplot[linestyle=none,algebraic,plotpoints=2000]{-1.2}{2.2}{x+3}
}%
\psframe*[linecolor=cyan,fillstyle=solid](-1,1)(2,5)
\end{psclip}
\psplot[algebraic,plotpoints=2000,yMaxValue=5.6%,linecolor=cyan
]{-2.3}{2.3}{x^2+1}
\psplot[algebraic,plotpoints=2000]{-3.5}{2.5}{x+3}
\psaxes{->}(0,0)(-3.5,-.9)(4,6.5)
\uput[-90](3.9,-.2){$x$}
\uput[-135](-.2,6.7){$y$}
\end{pspicture}
\end{document}


Looks like the problem is with functions like f(x)= ax + b.

Am i correct?

• what is the question? – David Carlisle Feb 15 '15 at 15:45
• Welcome to TeX.SX! As David said, it would be helpful to know what the question is. When you do edit your question, if you can, please a minimal working example (MWE). – Adam Liter Feb 15 '15 at 15:54
• I took the liberty of pasting the question from the deleted message you sent before. Just linking is not sufficient. – egreg Feb 15 '15 at 16:16
• I suppose the underlying question is: why replacing the line \psline[linestyle=none,algebraic,plotpoints=2000](-1,1)(-1,2)(2,5)(2,1) by \psplot[linestyle=none,algebraic,plotpoints=2000]{-1.2}{2.2}{x+3} makes the filling of the area stop working? No idea for my part… – Franck Pastor Feb 15 '15 at 17:11
• Yes David, perfect and thank you. I tried another functions and everything worked fine. But for functions like f(x) = ax + b, filling of the area don't works. – Ulysses Feb 15 '15 at 19:02

Wrap the curves used in the psclip inside a \pscustom, and make sure the enclose a space. To that end I've swapped the start/end points for the linear function x+3:

\documentclass{article}

\begin{document}

\begin{pspicture}(-3.5,-0.5)(4,7)
\begin{psclip}{
\pscustom[linestyle=none,algebraic,plotpoints=2000]{
\psplot{-1.2}{2.2}{x^2+1}%
\psplot{2.2}{-1.2}{x+3}
}
}%
\psframe*[linecolor=cyan,fillstyle=solid](-1,1)(2,5)
\end{psclip}
\psplot[algebraic,plotpoints=2000,yMaxValue=5.6%,linecolor=cyan
]{-2.3}{2.3}{x^2+1}
\psplot[algebraic,plotpoints=2000]{-3.5}{2.5}{x+3}
\psaxes{->}(0,0)(-3.5,-.9)(4,6.5)
\uput[-90](3.9,-.2){$x$}
\uput[-135](-.2,6.7){$y$}
\end{pspicture}

\end{document}

• Thanks a lot Werner. I enjoy this forum and it is helping me to write my Master's thesis about PSTricks and it's usage for courseware production. – Ulysses Feb 15 '15 at 19:22