Ubuntu Manpage: PCMPXY - This routine is normally not called directly by the user (though it can be). It is called by

NAME

       PCMPXY - This routine is normally not called directly by the user (though it can be). It is called by
       each of the routines PCHIQU, PCMEQU, and PCLOQU when the user has set the mapping flag ´MA´ nonzero to
       request mapping of characters from one X/Y coordinate system to another.

SYNOPSIS

       CALL PCMPXY (IMAP,XINP,YINP,XOTP,YOTP)

C-BINDING SYNOPSIS

       #include <ncarg/ncargC.h>
       void c_pcmpxy (int imap, float xinp, float yinp, float *xotp, float *yotp)

DESCRIPTION

IMAP (an input expression of type INTEGER) specifies which mapping is to be done. Whenever
Plotchar routines call PCMPXY, IMAP = ´MA´. The default version of PCMPXY recognizes the
following values of IMAP:

IMAP = 0

Type of mapping
None. When IMAP is zero, the routine PCMPXY is being asked for information about
its capabilities with respect to a particular mapping.

XINP
Input: the real equivalent of a possible value of IMAP about which information is
desired.

YINP
Output (real): 0. says that the mapping specified by XINP is not available, 1.
that it is available, 2. that its inverse is available, and 3. that both it and its
inverse are available.

IMAP = 1

Type of mapping
Ezmap projection.

XINP
Longitude, in degrees.

YINP
Latitude, in degrees.

IMAP = 2

Type of mapping
Rho/theta mapping.

XINP
Rho, in user units.

YINP
Theta, in degrees.

IMAP = 3

Type of mapping
Projection from an arbitrary parallelogram in 3-space to an image plane. This is
implemented using a package which is currently under development and is not yet
generally available.

XINP
A multiplier for a unit vector along one edge of the parallelogram.

YINP
A multiplier for a unit vector along an intersecting edge of the parallelogram.

IMAP = 4

Type of mapping
A version of the EZMAP projection that is intended to be used to label specific
points on the surface of the globe. When 'MA' = 4, use "0." for each of the
arguments XPOS, YPOS, and ANGD in calls to PCHIQU and PCMEQU. Initially, each
label is assumed to be placed at the point on the globe with latitude zero and
longitude zero and to be written along the equator. Three rotations are then
performed to move the label to the point (PLAT,PLON) in such a way that it makes an
angle PANG with the local eastward-pointing vector. Finally, the EZMAP routine
MAPTRA is called to project the label as specified by the current state of EZMAP.
The desired values of PANG, PLAT, and PLON (in degrees) are passed to PCMPXY in the
labelled common block PCMP04, which contains just those three variables, in that
order. Use the ncargex command to see the following relevant example: cpex10.

XINP
Longitude, in degrees.

YINP
Latitude, in degrees.

IMAP = 100

Type of mapping
The identity mapping, but returns 1.E12 outside a specified viewport. Used by the
utility Scrolled_title to do clipping at the edges of the viewport.

XINP
X coordinate, in the fractional system.

YINP
Y coordinate, in the fractional system.

other > 0

Type of mapping
The identity mapping.

XINP
Any real value.

YINP
Any real value.

other < 0

Type of mapping
An inverse mapping.

XINP
A mapped X coordinate.

YINP
A mapped Y coordinate.

Note: Values of IMAP less than or equal to zero are not currently used by Plotchar in calling
PCMPXY. The scheme described is the same as that used for the routine CPMPXY, in the NCAR
Graphics package Conpack. It is possible that, in the future, values of IMAP less than or
equal to zero will occur in calls to PCMPXY, so it is best to be prepared.

XINP and YINP
(input expressions of type REAL) specify the X and Y coordinates of a point to be mapped.

Note: When IMAP is less than or equal to zero (which cannot currently happen, but may someday
be possible), XINP and YINP are used differently, as shown above.

XOTP and YOTP
(output variables of type REAL) in which PCMPXY returns the mapped X and Y coordinates of the
point. If the point is not visible under the mapping selected (as, for example, when the
orthographic projection of Ezmap is being used and the point to be mapped is on the other
side of the globe), PCMPXY must return, as a signal that this is the case, whatever special
nonzero value has been given to the internal parameter ´OR´, so that the calling routine can
take appropriate action (to properly clip the character being drawn, for example).

Note: When IMAP is less than or equal to zero (which cannot currently happen, but may someday
be possible), XOTP and YOTP are used differently, as shown in the table above.

C-BINDING DESCRIPTION

       The C-binding argument descriptions are the same as the FORTRAN argument descriptions.

USAGE

       This routine is normally not called directly by the user (though it can be). It is called by each of the
       routines PCHIQU, PCMEQU, and PCLOQU when the user has set the mapping flag ´MA´ nonzero to request
       mapping of characters from one X/Y coordinate system to another. A call to PCMPXY has the following form:

            CALL PCMPXY (IMAP,XINP,YINP,XOTP,YOTP)

       The default version of PCMPXY does several useful mappings; a user version may be supplied to do others.

ACCESS

       To use PCMPXY or c_pcmpxy, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in
       that order.

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.