Area between graphs of two functions

Question

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}
\usepackage{pstricks-add}
\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}
\usepackage{pstricks-add}
\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?

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

score 3 · Accepted Answer · answered Feb 15 '15 at 18:28

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:

enter image description here

\documentclass{article}

\usepackage{pstricks-add}

\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

Area between graphs of two functions

1 Answers1