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##

Grid data

The 3D routines are designed for points in a grid format, with one sample,
datapoint, at each mesh intersection; the datapoints may originate from
either evaluating a function, see **set isosamples (p. )**, or reading a datafile,
see **splot datafile (p. )**. The term `"`isoline`"` is applied to the mesh lines for
both functions and data. Note that the mesh need not be rectangular in x
and y, as it may be parameterized in u and v, see **set isosamples (p. )**.
However, **gnuplot** does not require that format. In the case of functions,
'samples' need not be equal to 'isosamples', i.e., not every x-isoline
sample need intersect a y-isoline. In the case of data files, if there
are an equal number of scattered data points in each datablock, then
`"`isolines`"` will connect the points in a datablock, and `"`cross-isolines`"`
will connect the corresponding points in each datablock to generate a
`"`surface`"`. In either case, contour and hidden3d modes may give different
plots than if the points were in the intended format. Scattered data can be
converted to a {different} grid format with **set dgrid3d**.

The contour code tests for z intensity along a line between a point on a
y-isoline and the corresponding point in the next y-isoline. Thus a **splot**
contour of a surface with samples on the x-isolines that do not coincide with
a y-isoline intersection will ignore such samples. Try:

set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
set style function lp
set contour
set isosamples 10,10; set samples 10,10;
splot cos(x)*cos(y)
set samples 4,10; replot
set samples 10,4; replot

** Next:** Splot overview
** Up:** Splot
** Previous:** Matrix
** Contents**
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Ethan Merritt
2007-03-03