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Library -- Gnuplot Examples

1. Let's get started...
2. gnuplot-4.0
3. Print it out to PS printer
4. Examples
   • 3D plot
   • Draw Contour in 2D plot
   • Multiplot by using functions
   • Real Multiplot
   • Nuclear Chart

I love Gnuplot.

1. To get started, just type

   gnuplot [script-filename]
   
   

   Or if you are a beginner, after going into gnuplot (without filename), type

   help plot
   
   

   then you will see some explanations.

   $ gnuplot
   G N U P L O T
   Version 4.0 patchlevel 0
   ....
   Terminal type set to 'x11'
   gnuplot> help plot
   `plot` is the primary command for drawing plots with `gnuplot`. ...
   
   Syntax:
         plot {}
              { | {"" {datafile-modifiers}}}
              ...
   gnuplot> quit
   $
   

   One of the simplest sample is the following.

   $ gnuplot
   G N U P L O T
   Version 4.0 patchlevel 0
   ....
   Terminal type set to 'x11'
   gnuplot> plot sin(x)
   gnuplot> quit
   $
   

2. The current public version of gnuplot is Gnuplot-4.0. It supports greek letters, super- and sub-scripts in postscript output. (See "help postscript" for detail.)

   The figure below is a sample output of gnuplot4.0. The horizontal axis is the type of points, and the vertical axis is the type of lines. (They are not K⁺ momentum etc.!!) The script file is here, and its output EPS file is here.

   Line and point color is specified by the linetype.
   

   linetype(lt)-color and lt-dash correspondence in gnuplot 4.0
   lt	1	2	3	4	5	6	7	8	9	lt>10
   color	red	green	blue	magenta	lightblue	yellow	black	orange	grey	color @ mod(lt-1,9)+1
   dashed type	solid	dashed	short dashed	dotted	dot dashed	dot short dashed	...	...	...	dash @ mod(lt-1,9)+1

   
   The script file of color PS output is here, and its PS (eps) output is here.

   The above number-color correspondence in gnuplot-4.0 is the same in gnuplot-3.7. But the "linestyle" in 3.7 has to be replaced with "style line".

   set linestyle  1 lt 1 lw 6 # in gnuplot 3.7 script
   set style line 1 lt 1 lw 6 # in gnuplot 4.0 script
   	

3. In order to print out, you can type in gnuplot or write the following two lines in the script file.

   set term postscript
   set output "YOUR-OUTPUT-FILE-NAME"
   	

   and plot the figure. Then the figure is saved in the PS file which you specified.

   Interactive Session Example	Script Session Example
   $ gnuplot gnuplot> set term postscript gnuplot> set output "YOUR-OUTPUT-FILE-NAME" gnuplot> plot ... gnuplot> quit $ lpr YOUR-OUTPUT-FILE-NAME	$ gnuplot sin.plt $ lpr sin.ps with a test gnuplot script (sin.plt) as, set term postscript eps color enh "Times-BoldItalic" set title "sin(x)" set output "sin.ps" plot sin(x)

   
   You can put Greek and other character or symbols in postscript. Guide is here.

   ---

4. Now, I have some EXAMPLES. The first one is 3-d plot, and the second one is a naive way of plot multi-figures in one plot.

   ---

   • Example of 3D plot.
     Energy Surface of ¹²C, taken from our paper. By using "splot", we can draw surface and contours.
     • gnuplot script
     • data
     • Postscript (eps) output

     ---

   • Example to Draw Contour in 2D plot.
     Drawing contour in 2D plot is not a trivial task.... When we try to draw 2D contour by using "set view 0,0" (as in this script), y-axis is drawn in the right axis, and the contour line type cannot be specified, as in the left figure.
     Thus I usually do this in two steps. In the first step, I output the contour data in "tables", and in the second step, I plot that data.

     # 1st step
     set term "table"
     set output "temp.dat"
     splot ....
     # 2nd step
     set output "temp.eps"
     plot "temp.dat" using 1:2 with lines
     

     • gnuplot script
     • Postscript (eps) output

     ---

   • Example of Multiplot by using functions
     Impact parameter dependence of the IMFs in ¹⁹⁷Au+ ¹⁹⁷Au collision, taken from our paper. In gnuplot3.6beta, we can call functions from data, e.g., "plot 'datafile' using 1:(f($2))". This enables us to plot some figures in one plot, if you are patient. You can also use "set multiplot", when the figures are not connected.
     • gnuplot3.6 script
     • Postscript output

     ---

   • Example of Multiplot
     Effective free energy as a function of the chiral condensate is taken from our paper. In recent gnuplot (3.6beta340 or later), we can set bmargin (bottom margin), tmargin, lmargin, and rmargin in plot and multiplot. It means that, without any functional transform, drawing axis by hand, or fine tuning of the position of figures in multiplot, we can draw compactly packed figures.

     NX=1; NY=3
     DX=0.25; DY=0.25; SX=0.8; SY=0.6
     set bmargin DX; set tmargin DX; set lmargin DY; set rmargin DY
     set size SX*NX+DX*1.5,SY*NY+DY*1.8
     set multiplot
     # First  Figure
     set size SX,SY
     set origin DX,DY      ; plot ....
     # Second Figure
     set origin DX,DY+SY   ; plot ....
     # Third  Figure
     set origin DX,DY+SY*2 ; plot ....
     unset multiplot
     

     • gnuplot script
     • Postscript output

     In this figure, I applied another trick. In making color PS figures, we cannot control color and dashed type separately. I.e., when we select solid (set term post solid ...), all the lines become solid, and when we select dashed (set term post dashed ...), red line is solid, green line is dashed, and blue line becomes dotted.
     (In the next version of gnuplot, gnuplot-4.1 or current CVS version, we can select "red-dotted" or "blue-solid".)
     At present, I MODIFY the eps file itself.

         Default (black, dashed): /LT6 { PL [2 dl 2 dl 2 dl 4 dl] 0 0 0 DL } def
     --> Modified (black, solid): /LT6 { PL [] 0 0 0 DL } def
     

     Well, it would be easy in stream editor, sed.

     sed -f LT6-solid.sed Esurf.eps > Esurf-1.eps
     mv -f Esurf-1.eps Esurf.eps
     

     with a sed script (LT6-solid.sed),

     s/\/LT6 { PL \[2 dl 2 dl 2 dl 4 dl\] 0 0 0 DL } def/\/LT6 { PL \[\] 0 0 0 DL } def/
     

     • Packages of above (gnuplot and sed scripts, data, Makefile to modify line definition)

     ---

     
   • Nuclear Chart
     Combining awk and gnuplot, we can make nuclear chart as follows.
     • gnuplot script
     • awk file
     • Makefile
     • Input Data file
     • Postscript output
     • Package of the above

     ---

   • To be explained ...
     Folloing two figures are also drawn with gnuplot. I will explain later (some time ....)

     package

   ---

5. For special characters in postscript, please search for it in the "docs/psdocs/ps_guide.ps" in the gnuplot package.
6. I have two complains on the default version of gnuplot. One is that the dash length is too short (improved in gnuplot 4.0), and the second is that with "hist", gnuplot set both of the end points to zero, which is not always true especially in log plot. Then I usually use the following unofficial patch (for gnuplot 3.7.1) to make it my favorite.

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