|MATLAB Function Reference|
Color axis scaling
caxis controls the mapping of data values to the colormap. It affects any surfaces, patches, and images with indexed CData and CDataMapping set to scaled. It does not affect surfaces, patches, or images with true color CData or with CDataMapping set to direct.
sets the color limits to specified minimum and maximum values. Data values less than
cmin or greater than
cmax map to
cmax, respectively. Values between
cmax linearly map to the current colormap.
lets MATLAB compute the color limits automatically using the minimum and maximum data values. This is the default behavior. Color values set to
Inf map to the maximum color, and values set to -
Inf map to the minimum color. Faces or edges with color values set to
NaN are not drawn.
caxis manual and caxis(caxis)
freeze the color axis scaling at the current limits. This enables subsequent plots to use the same limits when
v = caxis
returns a two-element row vector containing the
cmax] currently in use.
uses the axes specified by
axes_handle instead of the current axes.
caxis changes the
CLimMode properties of axes graphics objects.
How Color Axis Scaling Works
Surface, patch, and image graphics objects having indexed CData and CDataMapping set to scaled map CData values to colors in the figure colormap each time they render.
CData values equal to or less than cmin map to the first color value in the colormap, and CData values equal to or greater than cmax map to the last color value in the colormap. MATLAB performs the following linear transformation on the intermediate values (referred to as
C below) to map them to an entry in the colormap (whose length is m, and whose row index is referred to as
(X,Y,Z) data for a sphere and view the data as a surface.
C have the range [-1 1]. Values of
C near -1 are assigned the lowest values in the colormap; values of
C near 1 are assigned the highest values in the colormap.
To map the top half of the surface to the highest value in the color table, use
To use only the bottom half of the color table, enter
which maps the lowest
CData values to the bottom of the colormap, and the highest values to the middle of the colormap (by specifying a cmax whose value is equal to cmin plus twice the range of the CData).
resets axis scaling back to autoranging and you see all the colors in the surface. In this case, entering
Adjusting the color axis can be useful when using images with scaled color data. For example, load the image data and colormap for Cape Cod, Massachusetts.
This command loads the image's data
X and the image's colormap
map into the workspace. Now display the image with
CDataMapping set to
scaled and install the image's colormap.
MATLAB sets the color limits to span the range of the image data, which is 1 to 192:
The blue color of the ocean is the first color in the colormap and is mapped to the lowest data value (1). You can effectively move sea level by changing the lower color limit value. For example,
CLimMode properties of axes graphics objects
Colormap property of figure graphics objects
Color Operations for related functions
Axes Color Limits for more examples
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