All of Octave's plotting functions use gnuplot
to handle the
actual graphics. There are two low-level functions, gplot
and
gsplot
, that behave almost exactly like the corresponding
gnuplot
functions plot
and splot
. A number of
other higher level plotting functions, patterned after the graphics
functions found in MATLAB version 3.5, are also available.
These higher level functions are all implemented in terms of the two
low-level plotting functions.
The ranges, using, title, and style arguments are optional, and the using, title and style qualifiers may appear in any order after the expression. You may plot multiple expressions with a single command by separating them with commas. Each expression may have its own set of qualifiers.
The optional item ranges has the syntax
[ x_lo : x_up ] [ y_lo : y_up ]
and may be used to specify the ranges for the axes of the plot,
independent of the actual range of the data. The range for the y axes
and any of the individual limits may be omitted. A range [:]
indicates that the default limits should be used. This normally means
that a range just large enough to include all the data points will be
used.
The expression to be plotted must not contain any literal matrices
(e.g. [ 1, 2; 3, 4 ]
) since it is nearly impossible to
distinguish a plot range from a matrix of data.
See the help for gnuplot
for a description of the syntax for the
optional items.
By default, the gplot
command plots the second column of a matrix
versus the first. If the matrix only has one column, it is taken as a
vector of y-coordinates and the x-coordinate is taken as the element
index, starting with zero. For example,
gplot rand (100,1) with linespoints
will plot 100 random values and connect them with lines. When
gplot
is used to plot a column vector, the indices of the
elements are taken as x values.
If there are more than two columns, you can choose which columns to plot with the using qualifier. For example, given the data
x = (-10:0.1:10)'; data = [x, sin(x), cos(x)];
the command
gplot [-11:11] [-1.1:1.1] \ data with lines, data using 1:3 with impulses
will plot two lines. The first line is generated by the command
data with lines
, and is a graph of the sine function over the
range -10 to 10. The data is taken from the first two columns of
the matrix because columns to plot were not specified with the
using qualifier.
The clause using 1:3
in the second part of this plot command
specifies that the first and third columns of the matrix data
should be taken as the values to plot.
In this example, the ranges have been explicitly specified to be a bit larger than the actual range of the data so that the curves do not touch the border of the plot.
gset
and gshow
commands from gnuplot
are available,
as is replot
.
Note that in Octave 2.0, the set
and show
commands were
renamed to gset
and gshow
in order to allow for
compatibility with the MATLAB graphics and GUI commands in a future
version of Octave. (For now, the old set
and show
commands do work, but they print an annoying warning message to try to
get people to switch to using gset
and gshow
.)
The gset
and gshow
commands allow you to set and show
gnuplot
parameters. For more information about the gset
and gshow
commands, see the documentation for set
and
show
in the gnuplot
user's guide (also available on line
if you run gnuplot
directly, instead of running it from Octave).
The replot
command allows you to force the plot to be
redisplayed. This is useful if you have changed something about the
plot, such as the title or axis labels. The replot
command also
accepts the same arguments as gplot
or gsplot
(except for
data ranges) so you can add additional lines to existing plots.
For example,
gset term tek40 gset output "/dev/plotter" gset title "sine with lines and cosine with impulses" replot "sin (x) w l"
will change the terminal type for plotting, add a title to the current plot, add a graph of sin (x) to the plot, and force the new plot to be sent to the plot device. This last step is normally required in order to update the plot. This default is reasonable for slow terminals or hardcopy output devices because even when you are adding additional lines with a replot command, gnuplot always redraws the entire plot, and you probably don't want to have a completely new plot generated every time something as minor as an axis label changes.
The command shg
is equivalent to executing replot
without
any arguments.
automatic_replot
to a nonzero value. Since this is fairly
inefficient, the default value is 0.
Note that NaN values in the plot data are automatically omitted, and Inf values are converted to a very large value before calling gnuplot.
The MATLAB-style two-dimensional plotting commands are:
plot (y)
where the argument is taken as the set of y coordinates and the x coordinates are taken to be the indices of the elements, starting with 1.
If more than one argument is given, they are interpreted as
plot (x, y, fmt ...)
where y and fmt are optional, and any number of argument sets may appear. The x and y values are interpreted as follows:
The fmt argument, if present is interpreted as follows. If fmt is missing, the default gnuplot line style is assumed.
@
or -@
specifiers.
"r"
, "g"
, "b"
, "m"
,
"c"
, or "w"
, it is interpreted as the plot color (red,
green, blue, magenta, cyan, or white).
The color line styles have the following meanings on terminals that support color.
Number Gnuplot colors (lines)points style 1 red * 2 green + 3 blue o 4 magenta x 5 cyan house 6 brown there exists
Here are some plot examples:
plot (x, y, "@12", x, y2, x, y3, "4", x, y4, "+")
This command will plot y
with points of type 2 (displayed as
`+') and color 1 (red), y2
with lines, y3
with lines of
color 4 (magenta) and y4
with points displayed as `+'.
plot (b, "*")
This command will plot the data in the variable b
will be plotted
with points displayed as `*'.
hold on
turns the hold state on. An argument of off
turns the hold state
off, and hold
with no arguments toggles the current hold state.
clg
is aliased to clearplot
for compatibility with MATLAB.
The commands gplot clear, gsplot clear, and replot
clear are equivalent to clearplot
. (Previously, commands like
gplot clear would evaluate clear
as an ordinary expression
and clear all the visible variables.)
gnuplot
subprocess. If you are using X11,
this will close the plot window.
Octave creates temporary data files for gnuplot
and then sends
commands to gnuplot
through a pipe. Octave will delete the
temporary files on exit, but if you are doing a lot of plotting you may
want to clean up in the middle of a session.
A future version of Octave will eliminate the need to use temporary files to hold the plot data.
The argument limits should be a 2, 4, or 6 element vector. The first and second elements specify the lower and upper limits for the x axis. The third and fourth specify the limits for the y axis, and the fifth and sixth specify the limits for the z axis.
With no arguments, axis
turns autoscaling on.
If your plot is already drawn, then you need to use replot
before
the new axis limits will take effect. You can get this to happen
automatically by setting the built-in variable automatic_replot
to a nonzero value.
bar
produces a bar graph.
If only one argument is given, it is taken as a vector of y-values and the x coordinates are taken to be the indices of the elements.
If two output arguments are specified, the data are generated but not plotted. For example,
bar (x, y);
and
[xb, yb] = bar (x, y); plot (xb, yb);
are equivalent.
gnuplot
's contour routines
before this will be very useful.
With one vector input argument, plot a histogram of the values with 10 bins. The range of the histogram bins is determined by the range of the data.
Given a second scalar argument, use that as the number of bins.
Given a second vector argument, use that as the centers of the bins, with the width of the bins determined from the adjacent values in the vector.
Extreme values are lumped in the first and last bins.
With two output arguments, produce the values nn and xx such
that bar (xx, nn)
will plot the histogram.
plot
above for a description of the arguments that
loglog
will accept.
plot
above for a description of the arguments
that semilogx
will accept.
plot
above for a description of the arguments
that semilogy
will accept.
If only one argument is given, it is taken as a vector of y-values and the x coordinates are taken to be the indices of the elements.
If two output arguments are specified, the data are generated but not plotted. For example,
stairs (x, y);
and
[xs, ys] = stairs (x, y); plot (xs, ys);
are equivalent.
The ranges, using, title, and style arguments are optional, and the using, title and style qualifiers may appear in any order after the expression. You may plot multiple expressions with a single command by separating them with commas. Each expression may have its own set of qualifiers.
The optional item ranges has the syntax
[ x_lo : x_up ] [ y_lo : y_up ] [ z_lo : z_up ]
and may be used to specify the ranges for the axes of the plot,
independent of the actual range of the data. The range for the y and z
axes and any of the individual limits may be omitted. A range
[:]
indicates that the default limits should be used. This
normally means that a range just large enough to include all the data
points will be used.
The expression to be plotted must not contain any literal matrices (e.g.
[ 1, 2; 3, 4 ]
) since it is nearly impossible to distinguish a
plot range from a matrix of data.
See the help for gnuplot
for a description of the syntax for the
optional items.
By default, the gsplot
command plots each column of the
expression as the z value, using the row index as the x value, and the
column index as the y value. The indices are counted from zero, not
one. For example,
gsplot rand (5, 2)
will plot a random surface, with the x and y values taken from the row and column indices of the matrix.
If parametric plotting mode is set (using the command
gset parametric, then gsplot
takes the columns of the
matrix three at a time as the x, y and z values that define a line in
three space. Any extra columns are ignored, and the x and y values are
expected to be sorted. For example, with parametric
set, it
makes sense to plot a matrix like
1 1 3 2 1 6 3 1 9 1 2 2 2 2 5 3 2 8 1 3 1 2 3 4 3 3 7
but not rand (5, 30)
.
The MATLAB-style three-dimensional plotting commands are:
x
, and y from meshdom
and
a matrix z corresponding to the x and y coordinates of
the mesh.
See the file `sombrero.m' for an example of using mesh
and
meshdom
.
"gnuplot"
. See section Installing Octave.
replot
to redisplay it with the new title.
replot
to redisplay it with the new
labels.
The following functions all require a version of gnuplot
that
supports the multiplot feature.
plot
function that works with
the multiplot version of gnuplot
to plot multiple plots per page.
This plot version automatically advances to the next subplot position
after each set of arguments are processed.
See the description of the plot function for the various options.
If the arguments are non-zero, multiplot
will set up multiplot
mode with xn, yn subplots along the x and y
axes. If both arguments are zero, multiplot
closes multiplot
mode.
"blank"
"all"
"north"
"south"
"east"
"west"
The arguments may be abbreviated to single characters. Without any
arguments, plot_border
turns borders off.
gnuplot
in multiplot mode and plots in location
given by index (there are cols by rows subwindows).
Input:
If only one argument is supplied, then it must be a three digit value specifying the location in digits 1 (rows) and 2 (columns) and the plot index in digit 3.
The plot index runs row-wise. First all the columns in a row are filled and then the next row is filled.
For example, a plot with 4 by 2 grid will have plot indices running as follows:
+-----+-----+-----+-----+ | 1 | 2 | 3 | 4 | +-----+-----+-----+-----+ | 5 | 6 | 7 | 8 | +-----+-----+-----+-----+
multiplot
function, otherwise this command just becomes an alias
to multiplot
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