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Can someone teach me how to plot this in LaTeX with TikZ?enter image description here

I figured out the code I need:

     \begin{tikzpicture}
     \begin{axis}[no marks,
     unbounded coords=jump,  
          axis lines=middle,
          xtick = \empty,
          ytick = \empty,
          xlabel = {$x$},
          ylabel = {$y$},
          xmajorgrids,]
     %PLOT OF THE FUNCTION--------------------------
      \addplot+[samples=101,thick,red] {1/(x^2-4)};
     %ASYMPTOTES---------------------------------------- 
     \addplot +[mark=none,style=dashed,color=black] coordinates {(2, -2.5) (2, 2.5)};
      \addplot +[mark=none,style=dashed,color=black] coordinates {(-2, -2.5) (-2, 2.5)};
      %DASHED SPACES------------------------------
      \path [pattern=north west lines, pattern color = gray]   (-5,-5) rectangle (-2,0);
      \path [pattern=north west lines, pattern color = gray]   (+5,-5) rectangle (+2,0);
      \path [pattern=north west lines, pattern color = gray]   (2,4) rectangle (-2,0);
     %POINTS---------------------
     \draw[fill=black] (0,-1/4) circle (0.05cm);
     \node at (1/3,-1/2) {$ A $}; 
     \end{axis}
     \end{tikzpicture}

This is the output: enter image description here

Now:

1) how put the xlabel down the axe?

2) Is there a way to have the point of intersection with axis automatically?

3) How ho have +2 and -2 in the dashed areas?
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  • I am not getting the output pictured above (with the shading) when I run the code. Could you check your code?
    – Dan
    Nov 8 '16 at 16:07
2

You have to hit the asymptotes for pgfplots to jump. The rest is just the function definition. The rest is given in your other question

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.14}
\begin{document}
\begin{tikzpicture}
\begin{axis}[no marks,unbounded coords=jump,
             axis lines=middle,ytick=\empty,xtick={-2,2},xmajorgrids]
\addplot+[samples=101] {1/(x^2-4)};
\end{axis}
\end{tikzpicture}
\end{document}

enter image description here

2
  • See edit please.
    – Andrea Leo
    Nov 8 '16 at 9:28
  • @AndreaLeo Please don't change questions along the way. You can always ask a new question such that the issue are contained. The questions you ask are all answered on the site and you can find them with a single search.
    – percusse
    Nov 8 '16 at 9:31
2

Adding onto Percusse's answer, to add shading, equation label, and dotted asymptotes you can do the following.

Code:

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}
\begin{document}
\begin{tikzpicture}
\begin{axis}[no marks,unbounded coords=jump,
             axis lines=middle,ytick=\empty,xtick={-2,2},xmajorgrids]
\addplot+[samples=101] {1/(x^2-4)};
\addplot +[mark=none,style=dashed,color=black] coordinates {(2, -2.5) (2, 2.5)};
\addplot +[mark=none,style=dashed,color=black] coordinates {(-2, -2.5) (-2, 2.5)};
\filldraw[fill=black, draw=black,opacity=.2,] (-5,-5) rectangle (-2,0);
\filldraw[fill=black, draw=black,opacity=.2,] (5,-5) rectangle (2,0);
\filldraw[fill=black, draw=black,opacity=.2,] (-2,0) rectangle (2,4);
\node[text width=3cm] at (4.5,1) 
    {\small{$f(x)=\frac{1}{x^2-4}$}};
\end{axis}
\end{tikzpicture}
\end{document}

This yields:

enter image description here

2
  • you can instead change the grid line style major x grid style={dashed}
    – percusse
    Nov 7 '16 at 23:58
  • See edits please.
    – Andrea Leo
    Nov 8 '16 at 9:27

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