GNUPlot Manual
GNUPlot Manual
GNUPlot Manual
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76 gnuplot 4.0 36 SET-SHOW<br />
36.33 Logscale<br />
Log scaling may be set on the x, y, z, x2 and/or y2 axes.<br />
Syntax:<br />
set logscale <br />
unset logscale <br />
show logscale<br />
where may be any combinations of x, y, z, and cb in any order, or x2 or y2 and where <br />
is the base of the log scaling. If is not given, then 10 is assumed. If is not given, then<br />
all axes are assumed. unset logscale turns off log scaling for the specified axes.<br />
Examples:<br />
To enable log scaling in both x and z axes:<br />
set logscale xz<br />
To enable scaling log base 2 of the y axis:<br />
set logscale y 2<br />
To enable z and color log axes for a pm3d plot:<br />
set logscale zcb<br />
To disable z axis log scaling:<br />
unset logscale z<br />
36.34 Mapping<br />
If data are provided to splot in spherical or cylindrical coordinates, the set mapping command should<br />
be used to instruct gnuplot how to interpret them.<br />
Syntax:<br />
set mapping {cartesian | spherical | cylindrical}<br />
A cartesian coordinate system is used by default.<br />
For a spherical coordinate system, the data occupy two or three columns (or using entries). The first<br />
two are interpreted as the azimuthal and polar angles theta and phi (or "longitude" and "latitude"), in<br />
the units specified by set angles. The radius r is taken from the third column if there is one, or is set<br />
to unity if there is no third column. The mapping is:<br />
x = r * cos(theta) * cos(phi)<br />
y = r * sin(theta) * cos(phi)<br />
z = r * sin(phi)<br />
Note that this is a "geographic" spherical system, rather than a "polar" one (that is, phi is measured<br />
from the equator, rather than the pole).<br />
For a cylindrical coordinate system, the data again occupy two or three columns. The first two are<br />
interpreted as theta (in the units specified by set angles) and z. The radius is either taken from the<br />
third column or set to unity, as in the spherical case. The mapping is:<br />
x = r * cos(theta)<br />
y = r * sin(theta)<br />
z = z<br />
The effects of mapping can be duplicated with the using filter on the splot command, but mapping<br />
may be more convenient if many data files are to be processed. However even if mapping is used, using<br />
may still be necessary if the data in the file are not in the required order.<br />
mapping has no effect on plot.<br />
world.dem:<br />
mapping demos.