Name: PGCONX
Purpose: contour map of a 2D data array (non rectangular)
Category: GRAPHICS
File: pgplot.src
Author: T.J. Pearson
Use: see description below.
Description:
SUBROUTINE PGCONX (A, IDIM, JDIM, I1, I2, J1, J2, C, NC, PLOT)
INTEGER IDIM, JDIM, I1, J1, I2, J2, NC
REAL A(IDIM,JDIM), C(*)
EXTERNAL PLOT
Draw a contour map of an array using a user-supplied plotting
routine. This routine should be used instead of PGCONT when the
data are defined on a non-rectangular grid. PGCONT permits only
a linear transformation between the (I,J) grid of the array
and the world coordinate system (x,y), but PGCONX permits any
transformation to be used, the transformation being defined by a
user-supplied subroutine. The nature of the contouring algorithm,
however, dictates that the transformation should maintain the
rectangular topology of the grid, although grid-points may be
allowed to coalesce. As an example of a deformed rectangular
grid, consider data given on the polar grid theta=0.1n(pi/2),
for n=0,1,...,10, and r=0.25m, for m=0,1,..,4. This grid
contains 55 points, of which 11 are coincident at the origin.
The input array for PGCONX should be dimensioned (11,5), and
data values should be provided for all 55 elements. PGCONX can
also be used for special applications in which the height of the
contour affects its appearance, e.g., stereoscopic views.
The map is truncated if necessary at the boundaries of the viewport.
Each contour line is drawn with the current line attributes (color
index, style, and width); except that if argument NC is positive
(see below), the line style is set by PGCONX to 1 (solid) for
positive contours or 2 (dashed) for negative contours. Attributes
for the contour lines can also be set in the user-supplied
subroutine, if desired.
Arguments:
A (input) : data array.
IDIM (input) : first dimension of A.
JDIM (input) : second dimension of A.
I1, I2 (input) : range of first index to be contoured (inclusive).
J1, J2 (input) : range of second index to be contoured (inclusive).
C (input) : array of NC contour levels; dimension at least NC.
NC (input) : +/- number of contour levels (less than or equal
to dimension of C). If NC is positive, it is the
number of contour levels, and the line-style is
chosen automatically as described above. If NC is
negative, it is minus the number of contour
levels, and the current setting of line-style is
used for all the contours.
PLOT (input) : the address (name) of a subroutine supplied by
the user, which will be called by PGCONX to do
the actual plotting. This must be declared
EXTERNAL in the program unit calling PGCONX.
The subroutine PLOT will be called with four arguments:
CALL PLOT(VISBLE,X,Y,Z)
where X,Y (input) are real variables corresponding to
I,J indices of the array A. If VISBLE (input, integer) is 1,
PLOT should draw a visible line from the current pen
position to the world coordinate point corresponding to (X,Y);
if it is 0, it should move the pen to (X,Y). Z is the value
of the current contour level, and may be used by PLOT if desired.
Example:
SUBROUTINE PLOT (VISBLE,X,Y,Z)
REAL X, Y, Z, XWORLD, YWORLD
INTEGER VISBLE
XWORLD = X*COS(Y) ! this is the user-defined
YWORLD = X*SIN(Y) ! transformation
IF (VISBLE.EQ.0) THEN
CALL PGMOVE (XWORLD, YWORLD)
ELSE
CALL PGDRAW (XWORLD, YWORLD)
END IF
END
Note: This subroutine is only callable from Fortran, not from C.
Updates: Oct 16, 1998: JPT automatically extracted from source.