demcmap(Z) sets the
colormap and color axis limits based on the elevation data limits
derived from input argumentZ.

The default colormap assigns shades of green and brown
for positive elevations, and various shades of blue for negative elevation
values below sea level.

The number of colors assigned to land and to sea
are in proportion to the ranges in terrain elevation and bathymetric
depth and total 64 by default. The color axis limits are computed
such that the interface between land and sea maps to the zero elevation
contour.

The colormap is applied to the current figure and
the color axis limits are applied to the current axes.

demcmap(Z,ncolors) creates
a colormap of length ncolors.

demcmap(Z,ncolors,cmapsea,cmapland) assigns cmapsea and cmapland to
elevations below and above sea level respectively.

demcmap('inc',Z,deltaz) chooses
number of colors and color axis limits such that each color approximately
represents the increment of elevation deltaz.

The literal string 'inc' signals demcmap that
the first argument after Z will be deltaz.

demcmap('inc',Z,deltaz,cmapsea,cmapland)assigns cmapsea and cmapland to
elevations below and above sea level respectively.

[cmap,climits]
= demcmap(___) returns colormap cmap and
color axis limit climits, using any of the above
syntaxes, but does not apply them to figure or axes properties.

Even if only one output argument is specified, no
change occurs to figure or axes properties.

Custom RGB colormaps, cmapssea; cmapland ,
of differing lengths are used to populate figure colormap by interpolation.
The colors in each colormap map to the land and sea regions of the
map. Fewer colors have been specified in total than the default number
of 64. demcmap determines maximum and minimum elevation
data limits internally as shown in the below example when the first
argument is the elevation data grid.

The following demcmap example
controls the color quantization by choosing an optimal number of colors
such that each color represents an elevation increment of approximately
2000 .

Terrain elevation limits specified as a vector or matrix. If Z is
a 2 element vector, then it specifies the minimum and maximum limits
of terrain elevation data; ordering is not important. If Z is
a matrix, then it specifies an elevation grid in which positive and
negative values represent points above and below sea level respectively.
The above two syntaxes for demcmap are identical
in their effect on the figure colormap and axes properties.

Data Types: single | double | int8 | int32 | uint8 | uint16 | uint32

RGB colormaps specified as mx3 arrays containing any
number of rows. The two colormaps need not be equal in length. They
serve as the basis set for populating the figure colormap by interpolation.

cmapsea and cmapland replace
the default colormap. The default colormap for land or sea can be
retained by providing an empty matrix in place of either colormap
matrix.

That part of the figure colormap assigned to negative elevations
is derived from cmapssea; cmapland plays
a similar role for positive elevations.

The increment of elevation specified as a scalar. The color
quantization of the default or user supplied colormap is adjusted
such that each discrete color approximately represents a deltaz increment
in elevation.

RGB colormap returned as a matrix constructed for the figure
colormap. Supply output arguments when you want to obtain the colormap
and color axis limits without applying them automatically to the figure
or axes properties. These properties remain unchanged even if only
one output (cmap) is specified.

Color axis limits returned as a vector. climits may
differ somewhat from those derived from input argument Z due
to the quantization which results from fitting a limited number of
colors over the range limit of the elevation data.

Supply output arguments when you want to obtain the colormap
and color axis limits without applying them automatically to the figure
or axes.

If the elevation grid data contains both positive and negative
values, then the computed colormap, cmap, has a
"sea" partition of length nsea and
"land" partition of length nland. The sum of nsea and nland equals
the total number of entries in the computed colormap. The actual
values of nsea and nland depend
upon the number of entries and the relative range of the negative
and positive limits of the elevation data. The sea partition consists
of rows 1 through nsea, and the land partition
consists of rows nsea + 1 through ncolors.
The sea and land partitions of the figure colormap are populated with
colors interpolated from the basis RGB colormaps, cmapsea and cmapland.
In the figure below, the sea and land 3x3 RGB colormaps shown are
the default colors used by demcmap to populate
the figure colormap when no user specified colormaps are provided.

If the elevation grid data contains only positive or negative
values, then the figure colormap is derived solely from the corresponding
sea or land colormap.