not so FAQ

• Legend
• Tics
• Label
• 2-D Plot
  • 
    fixed-size plot

  • 
    both sides of Y-axes

  • 
    erase axes

  • 
    fixed aspect ratio figure

  • 
    zero axis

  • 
    small bars of error bars

  • 
    larger letters

  • 
    smooth curves.

  • 
    points on border

  • 
    several figures

  • 
    grid at minor tics

  • 
    two axes

  • 
    grid at an arbitrary position

  • 
    figure in figure

  • 
    bar-chart

  • 
    Align two figures

  • 
    normal probability axis
• 3-D Plot
• Polar Coordinate
• Parametric Functions
• Data File
• After Plotting
• Miscellaneous Stuff

About 2-Dimensional Plot (No.3)

I want to draw several figures on one drawing.

There are two methods to make a drawing which contains several
figures. The first one is to use multiplot . The other
way is to use the EPS format, then those files in this format are
gathered by TeX or some drawing tools. Here we explain the
multiplot command.

With the command set multiplot you enter the multi-plot
mode, and the gnuplot command prompt becomes multiplot> .
In this mode a new figure overlaps the old one. The next example
shows the overlapping plot of three functions, y=x, y=x*x, and
y=x*x*x.

gnuplot> set multiplot
multiplot> plot x
multiplot> plot x*x
multiplot> plot x*x*x
multiplot> set nomultiplot

Gnuplot determines the range, tics, and size of figure automatically
for each plotting, then the plot gets into a mess. Let’s try to fix
the X and Y ranges [-10:10], and erase the legends by no key
command since they overlap.

gnuplot> set xrange [-10:10]
gnuplot> set yrange [-10:10]
gnuplot> set nokey
gnuplot> set multiplot
multiplot> plot x
multiplot> plot x*x
multiplot> plot x*x*x
multiplot> set nomultiplot

Well, it’s much better. But such thing can be done by usual plotting
procedures. With the multiplot command you can draw
several figures in one page by moving the origin of each figure.
To do that, use set size and set origin
commands.

As an example of multiplot, four Lissajous’ figures are plotted in
one drawing. The Lissajous’s figure can be drawn by a parametric
representaion of two functions, x=sin(n*t) and y=sin(m*t). Here we
draw the case of n=3,5 and m=2,4.

gnuplot> set parametric

dummy variable is t for curves, u/v for surfaces
gnuplot> set noxtic
gnuplot> set noytic
gnuplot> set nokey
gnuplot> set size square 0.3,0.3
gnuplot> set rmargin 0
gnuplot> set lmargin 0
gnuplot> set tmargin 0
gnuplot> set bmargin 0
gnuplot> set multiplot
multiplot> set origin 0.1,0.1
multiplot> plot sin(3*t),cos(2*t)
multiplot> set origin 0.1,0.5
multiplot> plot sin(3*t),cos(4*t)
multiplot> set origin 0.5,0.1
multiplot> plot sin(5*t),cos(2*t)
multiplot> set origin 0.5,0.5
multiplot> plot sin(5*t),cos(4*t)
multiplot> set nomultiplot

In order to make those figures the same size, the tics are erased by
noxtic and noytic , and the four margins are
set to be zero.

Usually it is difficult to adjust the position of each figure
appropriately. There is no easy way to determine the values of
origin , and you have to do
it by “trial-and-error”. When your figure has tics and labels, the
size of figure also depends on them. The adjustment of the
positions becomes very severe for this case.

I want to draw a grid at minor tics.

The command set grid makes
grids at the major tics position. In order to make them at the minor
tics :

gnuplot> set mxtics 5
gnuplot> set mytics 5
gnuplot> set grid xtics ytics mxtics mytics

This gives five grids at the minor tics between the major ones. You
can specify the grid position by xtics ... mytics
options of the set grid command. If set grid
noxtics noytics mxtics mytics , the grids appear at the minor
tics position only (but I guess no one likes such a graph
though…)