Plot data file with PGFPlot

Tikz and pgfplot can plot data file in Tex.

\begin{figure}

\begin{center}

\begin{tikzpicture}[scale=0.3]

\begin{axis}[xlabel=nstep, ylabel=WaveHeight]

\addplot[mark=none] file {case14.data};   % Here is the data file

\addplot[color=green,mark=none] file {case14xb.data};

\legend{True, Predicted};

\end{axis}

\end{tikzpicture}

\begin{tikzpicture}[scale=0.3]

\begin{axis}[xlabel=nstep, ylabel=error(2-norm)]

\addplot[mark=none] file {case14err.data};

\end{axis}

\end{tikzpicture}

\end{center}

\caption{(a)True and predicted wave height at the domain center; (b)2-norm of numerical error on the whole domain}

\end{figure}

The data file's format can be multiple columns separated by space. Each column is for one variable. Such as
# data file
0.00001 2.123243
0.00003 3.123452
......

Sometimes, Matlab's fprintf function may help to generate such data file.

For example:

a=load('err14.dat');

fid = fopen('case14err.data','w');

b=1/650:6.5/650:6.5;

y=[b ; a];

fprintf(fid,'%1.5f %1.5f\n', y);

fclose(fid);