Math & Science ⇒ Drawing function in tikzpicture

[m3talac]

I have to draw function with \plot but it says "Dimension too large", this is my code:

Code: Select all

\begin{tikzpicture}
\begin{axis}[grid=major, xmin=0, xmax=3, ymin=-1.5, ymax=1.5, xlabel=$t$, ylabel=$x(t), y(t)$, scale=0.3]
\plot[blue] plot[samples=100, smooth] expression{(1 + 2 * x)*exp(-2*x) * sin(280* 3.14 * x)};
\plot[red, dashed] plot[samples=100, smooth] expression{ (1+2*x) * exp(-2*x)};
\end{axis}
\end{tikzpicture}

Hope you can help me because i need it in few days, there are picture how it should look:

plot.jpg (47.71 KiB) Viewed 32417 times

and this are functions:

formula.jpg (15.87 KiB) Viewed 32417 times

Thanks.

[Stefan Kottwitz]

Hi,

welcome to the forum!

I would use pgfplots for this. Have a look at the pgfplots gallery for examples.

To avoid that "Dimension too large" error, you can restrict the y value as I do here:

Code: Select all

\documentclass[border=10pt]{standalone} 
\usepackage{pgfplots}
\pgfplotsset{%
  every tick label/.append style = {font=\tiny},
  every axis label/.append style = {font=\scriptsize}
}
\begin{document}
\begin{tikzpicture}
  \begin{axis}[grid=major, xmin=0, xmax=3, ymin=-1.1, ymax=1.1,
    xlabel=$t$, ylabel={$x(t), y(t)$},
    xtick = {0,0.5,...,3}, ytick = {-1,-0.5,...,1},
    scale=0.3, restrict y to domain=-1:1]
    \addplot[blue, samples=100, smooth, unbounded coords=discard]
      plot (\x, { 1 + 2 * \x)*exp(-2*\x) * sin(280* 3.14 * \x) });
    \addplot[red, dashed, samples=100, smooth]
      plot (\x, { (1+2*\x) * exp(-2*\x) } );
    \addplot[red, dashed, samples=100, smooth]
      plot (\x, { -(1+2*\x) * exp(-2*\x) } );
  \end{axis}
\end{tikzpicture}
\end{document}

plot.png (15.7 KiB) Viewed 33943 times

Stefan

[GKS]

Hello,

I would like to mention, that there is a little mistake/typo in your code, Stefan_K. It should be

Code: Select all

sin(180* 3.14 * \x)

Then the Graph fits to the so called envelope.

For better convenience

Code: Select all

\documentclass[border=10pt]{standalone}
    \usepackage{pgfplots}
    \pgfplotsset{%
      every tick label/.append style = {font=\tiny},
      every axis label/.append style = {font=\scriptsize}
    }
    \begin{document}
    \begin{tikzpicture}
      \begin{axis}[grid=major, xmin=0, xmax=3, ymin=-1.1, ymax=1.1,
        xlabel=$t$, ylabel={$x(t), y(t)$},
        xtick = {0,0.5,...,3}, ytick = {-1,-0.5,...,1},
        scale=0.3, restrict y to domain=-1:1]
        \addplot[blue, samples=100, smooth, unbounded coords=discard]
          plot (\x, { 1 + 2 * \x)*exp(-2*\x) * sin(180* 3.14 * \x) });
        \addplot[red, dashed, samples=100, smooth]
          plot (\x, { (1+2*\x) * exp(-2*\x) } );
        \addplot[red, dashed, samples=100, smooth]
          plot (\x, { -(1+2*\x) * exp(-2*\x) } );
      \end{axis}
    \end{tikzpicture}
    \end{document}

Greeetings GKS

[Stefan Kottwitz]

Hi GKS,

thank you for the correction!

And welcome to the forum,

Stefan