GNUPlot Manual

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