Color gradients
Syntax: |
DENSITY { x y } z { p1 p2 }
|
Qualifiers: |
\LEGEND, \HISTOGRAM, \PARTIAL, \XPROFILE, \YPROFILE, \BORDER, \AXES, \RESET
|
Defaults: |
if
|
Color gradients is the default density type. No qualifiers are needed to produce this type of drawing. The range of values of the matrix is divided into ten (10) equal levels, and a different color is associated with each level. By default, a value is interpolated at each pixel location within the matrix region so as to give smoothly joined regions.
Input variables
If z
is a vector, the parameters x
and y
are expected and must be vectors. x
and y
are assumed to represent a scattered set
of points, where z[i]
is the altitude corresponding to the location
(x[i],y[i])
. A matrix is interpolated on these scattered points by means of a Thiessen
triangulation of the plane. The three vectors must be the same length.
If z
is a matrix, the parameters x
and y
default to
[1;2;3;...]
, but if entered they must be vectors. Each matrix element,
z[i,j]
, is associated with the coordinates
(x[j],y[i])
. The length of x
must be equal to
the number of columns of z
and the length of
y
must be equal to the number
of rows. The vectors x
and y
are used for scaling the axes.
Not interpolated gradients
If the \HISTOGRAM
qualifier is used, each
data location is represented by a rectangle of color, centered on the data location.
The regions are not smoothly joined.
Changing the range of values
The optional parameters p1
and p2
can be used to broaden or shrink the range of
data values. If zmax
is the maximum value of the data and
zmin
is the minimum value of the data, the full color range
will be from a minimum of p1*(zmax-zmin)+zmin
to a maximum of p2*(zmax-zmin)+zmin
.
If z
is a data value and if
z < p1*(zmax-zmin)+zmin
,
that data value is treated as zmin
.
If z > p1*(zmax-zmin)+zmin
,
that data value is treated as zmax
.
The default values are: p1=0
and
p2=1
.
Legend
If the \LEGEND
qualifier is used, a legend is
drawn along the right side of the axes. The legend requires the right end of the
x-axis to be set to 75%
of the window, that is,
XUPPERAXIS
is set to 75%
.
When a y-profile is drawn, using the
\YPROFILE
qualifier, the right edge of the axis box must allow space for the
profile as well as a possible legend. If a y-legend profile and a legend are present, then
XUPPERAXIS
is set to 65%
. If a y-legend profile is present but
not a legend, then XUPPERAXIS
is set to 85%
.
By default, XUPPERAXIS
is reset to its former value after the
DENSITY
command. If the /-RESET
qualifier is used, the
axis location is not reset.
Examples
These examples use the following vectors.
X=[ 1; 0; 1; 0; .2; .3; .5; .8] Y=[ 5; 5; 0; 0; 1;1.5; 2.5; 4] Z=[ 10; 10; 10; 10; -100; 10; -100; 500]
SET COLORMAP THERMAL
DENSITY\LEGEND X Y Z
SET COLORMAP RAINBOW
DENSITY\LEGEND X Y Z