ncl_cpmpxy - Man Page

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

IMAP

(INTEGER, input) is zero if the object of the call is  to ask CPMPXY about its mapping capabilities, greater than  zero if the object of the call is to do a forward mapping,  and less than zero if the object of the call is to do an  inverse mapping. When IMAP is non-zero, its absolute value  matches the current value of the parameter 'MAP' and  identifies the mapping to be used.

XINP

(REAL, input) is used in one of three ways:

• When IMAP is zero, the value INT(XINP) is the index of a  mapping about which CPMPXY is being asked to supply  information.
• When IMAP is greater than zero, XINP is the X coordinate of  a point on the contour plot. If 'XC1' = 'XCM' (the default  situation), then XINP will lie in the range from 1 to M,  where M is the first dimension of the array being contoured  (equal to the value of the parameter 'ZDM'); in this case,  the X coordinate will have the same range as the first  index of the data array. If the user sets 'XC1' unequal to  'XCM', then XINP will lie in the range from 'XC1'  (corresponding to an index value of 1) to 'XCM'  (corresponding to an index value of M).
• When IMAP is less than zero, XINP is the X coordinate of a  point on the contour plot, in a coordinate system  consistent with the current window, as specified by  arguments 5 through 8 of the last call to the SPPS routine  SET or by the equivalent call to GKS.

YINP

(REAL, input/output) is used in one of three ways:

• When IMAP is zero, CPMPXY is expected to return one of the  following values of YINP: YINP = 0. indicates that neither  the forward nor the inverse transformation is defined. YINP  = 1. indicates that the forward transformation is defined,  but the inverse is not. YINP = 2. indicates that the  forward transformation is not defined, but the inverse is.  YINP = 3. indicates that both the forward and the inverse  transformations are defined.
• When IMAP is greater than zero, YINP is the Y coordinate of  a point on the contour plot. If 'YC1' = 'YCN' (the default  situation), then YINP will lie in the range from 1 to N,  where N is the second dimension of the array being  contoured (equal to the value of the parameter 'ZDN'); in  this case, the Y coordinate will have the same range as the  second index of the data array. If the user sets 'YC1'  unequal to 'YCN', then YINP will lie in the range from  'YC1' (corresponding to an index value of 1) to 'YCN'  (corresponding to an index value of N).
• When IMAP is less than zero, YINP is the Y coordinate of a  point on the contour plot, in a coordinate system  consistent with the current window, as specified by  arguments 5 through 8 of the last call to the SPPS routine  SET or by the equivalent call to GKS.

XOTP and YOTP

(REAL, output) are used in one  of two ways:

• If IMAP is greater than zero, XOTP and YOTP are the X and Y  coordinates of a point on the contour plot, in a coordinate  system consistent with the current window, as specified by  arguments 5 through 8 of the last call to the SPPS routine  SET or by the equivalent call to GKS.

• When IMAP is less than zero, XOTP and YOTP are the X and Y  coordinates of a point on the contour plot. If 'XC1' =  'XCM' (the default situation), then XOTP will lie in the  range from 1 to M, where M is the first dimension of the  array being contoured (equal to the value of the parameter  'ZDM'); in this case, the X coordinate will have the same  range as the first index of the data array. If the user  sets 'XC1' unequal to 'XCM', then XOTP will lie in the  range from 'XC1' (corresponding to an index value of 1) to  'XCM' (corresponding to an index value of M). Similarly, if  'YC1' = 'YCN' (the default situation), then YOTP will lie  in the range from 1 to N, where N is the second dimension  of the array being contoured (equal to the value of the  parameter 'ZDN'); in this case, the Y coordinate will have  the same range as the second index of the data array. If  the user sets 'YC1' unequal to 'YCN', then YOTP will lie in  the range from 'YC1' (corresponding to an index value of 1)  to 'YCN' (corresponding to an index value of N).

  In any case, if the point (XINP,YINP) cannot be mapped for  any reason, some recognizable impossible value should be  returned for both of XOTP and YOTP and the internal  parameter 'ORV' should be given that value, thereby  allowing Conpack routines that call CPMPXY to determine  whether or not a point being projected is visible or not.  The value used for this purpose by the Ezmap routines  MAPTRA and MAPTRI is 1.E12.

CPMPXY is not to be called by the user. It is called by  Conpack when the parameter 'MAP' is non-zero. Each call is  intended 1) to inquire whether a given mapping is defined  by CPMPXY, or 2) to map the X and Y coordinates of a single  point, whose position is known relative to the data grid,  to X and Y coordinates in some other coordinate system or  3) (as of version 3.1.3) to do the inverse mapping. The  default version of CPMPXY is as follows:

SUBROUTINE CPMPXY (IMAP,XINP,YINP,XOTP,YOTP)
  IF (IMAP.EQ.0) THEN
    IF (INT(XINP).GE.1.AND.INT(XINP).LE.3) THEN
      YINP=3.
    ELSE
      YINP=0.
    END IF
  ELSE IF (ABS(IMAP).EQ.1) THEN
    IF (IMAP.GT.0) THEN
      CALL MAPTRA (YINP,XINP,XOTP,YOTP)
    ELSE
      CALL MAPTRI (XINP,YINP,YOTP,XOTP)
    END IF
  ELSE IF (ABS(IMAP).EQ.2) THEN
    IF (IMAP.GT.0) THEN
      XOTP=XINP*COS(.017453292519943*YINP)
      YOTP=XINP*SIN(.017453292519943*YINP)
    ELSE
      XOTP=SQRT(XINP*XINP+YINP*YINP)
      YOTP=57.2957795130823*ATAN2(YINP,XINP)
    END IF
  ELSE
    XOTP=XINP
    YOTP=YINP
  END IF
  RETURN
END

When CPMPXY is called with IMAP = 0, it assumes it is being  asked to return information about its mapping capabilities.  XINP is assumed to have been given the value REAL(I), where  I is the index of a mapping about which information is  desired. CPMPXY sets YINP to indicate whether the mapping  selected by I is implemented or not and whether its inverse  is implemented or not. In the case of the default version  of CPMPXY, mappings 1 through 3 are completely implemented  (both forward and reverse), so a "3." is returned as the  value of YINP; other mappings are not implemented at all,  so a "0." is returned as the value of YINP.

When CPMPXY is called with IMAP = 1, the incoming X and Y  coordinates are assumed to represent longitude and  latitude, respectively; the Ezmap routine MAPTRA is called  to find the X and Y coordinates of the projection of the  specified point on the globe, and those coordinates are  returned as the outgoing X and Y coordinates. When IMAP =  -1, the incoming X and Y coordinates are assumed to be the X  and Y coordinates of a projected point; the Ezmap routine  MAPTRI is called to find the longitude and latitude of the  original point on the globe, and those values are returned  as the outgoing X and Y coordinates.

When IMAP = 2, the incoming X and Y coordinates are assumed  to represent rho and theta (in degrees) in polar  coordinates; from these are computed the output X and Y  coordinates. When IMAP = -2, the incoming X and Y  coordinates are used to compute rho and theta and those  values are returned.

If IMAP is anything else, the input X and Y coordinates are  simply returned as the output X and Y coordinates.

A user version of CPMPXY can be made to do any desired  mapping. It should also be made, when IMAP = 0, to return  correct information about its own capabilities.

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

Online: conpack, cpback, cpchcf, cpchcl, cpchhl, cpchil, cpchll, cpcica, cpclam, cpcldm, cpcldr, cpcltr, cpcnrc, cpdrpl, cpezct, cpgetc, cpgeti, cpgetr, cplbam, cplbdr, cpmviw, cpmvrw, cppkcl, cppklb, cprect, cprset, cpscae, cpsetc, cpseti, cpsetr, cpsps1, cpsps2, ncarg_cbind

Hardcopy: NCAR Graphics Contouring and Mapping Tutorial

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