Getting Hard Copy

 

After going through the previous sections, you probably would like to get your plots printed on paper or imported into your document. In this section you will learn some of the ways to accomplish these tasks.

Output to Graphic Files or Printers

 

gnuplot has support for a rather large variety of printers. To see the list of supported printers (and other graphic formats), type set term at the gnuplot command line. The command set term term-type tells gnuplot that the subsequent plots are to be generated on term-type . If you are using a Laserjet II compatible printer, you can use hpljii. If you are printing on a PostScript printer, you can use postscript. There are options for controlling the orientation, fonts, font sizes, etc. For the details, check the online help or the gnuplot manual.

Once you have set the terminal type to the correct device, you need to tell gnuplot where you want to send the output. This is done by set output ` filename ', where filename is the name of file where the plot is to be stored. On Unix systems, you can do set term `| lpr -Php1' to send the plot directly to the printer (the -Php1 is the lpr option for selecting the printer). However, the plot won't be printed until you exit gnuplot.

Here is an example for plotting the function to the file bivnorm.ps and then printing it out:

  f(x,y)=exp(-.5*(x**2+y**2))/(2*pi)
  set title 'Bivariate Normal Density'
  set xlabel 'x'
  set ylabel 'y'
  splot [-4:4] [-4:4] f(x,y)   # check the plot on screen
  set term post           # set terminal type to postscript
  set output 'bivnorm.ps' # set the output file to bivnorm.ps
  replot                  # regenerate last plot
  set term x11            # reset terminal type to the screen
  !lpr -Php1 bivnorm.ps

The last line starts with !, which tells gnuplot that what follows is a system command. If you are on a PC and want to generate the plot to the Laserjet format, the last five lines can be replaced by

  set term hpljii 150     # set terminal type to Laserjet II
  set output 'bivnorm.hp' # set the output file to bivnorm.hp
  replot                  # regenerate last plot
  set term vgalib         # reset terminal type to the screen
  !copy bivnorm.hp prn /b

If you want the plot to be printed directly to the printer, use prn instead of a filename in the set term command. Just typing set output without any argument sets output to standard output.

If you want to generate several plots in the same file, you can use the clear command to tell gnuplot to go to a new page. If you set terminal to a screen device, the clear command will clear the graphics screen/window.

There are several ways to put multiple plots on the same page, none of which is trivial. If you are using a word processor or desktop publishing program that can import one of the graphics formats supported by gnuplot, (e.g. pbm, eps, aifm, hpgl, dxf, etc.) this should not be a problem. If you are using dvips to produce TeX/LaTeX output, you can use the psfig macros to put multiple PostScript files on the same page. If you are using LaTeX, the instructions in Section  should help you achieve this.

Including Plots in A LaTeX document

 

  
Figure: This the example plot generated with the latex terminal type in gnuplot.

There is a latex terminal type in gnuplot, which lets you generate plots in LaTeX's picture environment format. Here's an example:

  f(x)=sin(exp(x**2))
  g(x)=cos(exp(x**2))
  set term latex
  set samples 500
  set output 'example.tex'
  set title 'An Example of Plotting in \LaTeX\ with {\sf gnuplot}'
  set format y '$%g$'
  set xtics ('$-\frac{\pi}{2}$' -pi/2, '$-\frac{\pi}{4}$' -pi/4,\
             '0' 0, '$\frac{\pi}{4}$' pi/4, '$\frac{\pi}{2}$' pi/2)
  set xrange[-pi/2:pi/2]
  plot f(x) title '$\sin e^{x^2}$', g(x) title '$\cos e^{x^2}$'

Then in the LaTeX document, where you want to insert the plot, do the following:

  \begin{figure}
  \begin{center}
  \end{center}
  \caption{This the example plot generated with the \cmd{latex} 
           terminal type in {\sf gnuplot}.}
  \end{figure}

You should get the plot shown in Figure .

Note that the number of points to be evaluated is set to 500. This is done to improve the appearance of the curves on paper. gnuplot's default setting of 100 points may be sufficient for viewing on the screen, but the resolutions of printers are usually much higher than that of screen.

For more details, please refer to the document LaTeX and the GNUPLOT Plotting Program by David Kotz, which is included with the gnuplot\ distribution.

If you are using a PostScript device for LaTeX output, there is a pslatex terminal type, which uses LaTeX to typeset the title, labels, etc. and PostScript specials for the plot. The quality of the plot is better than the plain LaTeX's native picture environment. The output from gnuplot with the pslatex terminal type can be inserted into your LaTeX document the same way as described above. However, most dvi previewers don't support the PostScript specials. Thus you won't be able to preview the plot with the rest of the document.

There are a few drawbacks of using the latex terminal type. For one, the plot is drawn with commands in LaTeX's picture environment. Lines can only be drawn in certain slopes. Thus the appearance of the plot can be less than satisfying. For another, it is almost impossible to import a three-dimensional surface plot into LaTeX with it because it will almost always exceed LaTeX's capacity. Using pslatex instead of latex usually doesn't help. An alternative is the eepic terminal type. eepic is an extended picture environment for LaTeX. Figure  was created with the eepic terminal type. To use eepic, you need the files epic.sty and eepic.sty (available from any Comprehensive TeX Archive Network sites, e.g., pip.shsu.edu). You need to load these two style files as options in the documentstyle statement. Then you can import the output from gnuplot as described above.