NAME

       Bivar - Provides bivariate interpolation and smooth surface fitting for values given at
       irregularly distributed points.  The resulting interpolating function and its first-order
       partial derivatives are continuous.  The method employed is local, i.e. a change in the
       data in one area of the plane does not affect the interpolating function except in that
       local area.  Also, the method gives exact results when all points lie in a plane.

SYNOPSIS

       IDBVIP      Produces interpolated values at points (XI(I), YI(I)), I=1,...,NIP.  This is
                   useful for filling in missing data points on a grid.

       IDSFFT      Performs smooth surface fitting when the projections of the data points in the
                   X-Y plane are irregularly distributed in the plane.

       IDPLTR      Plots the triangulation of the data points.

       IDGETI      Retrieves the integer value of a Bivar parameter.

       IDGETR      Retrieves the real value of a Bivar parameter.

       IDSETI      Provides a new integer value for a Bivar parameter.

       IDSETR      Provides a new real value for a Bivar parameter.

C-BINDING SYNOPSIS

       c_idbvip,
       c_idsfft
       c_idpltr
       c_idgeti
       c_idgetr
       c_idseti
       c_idsetr

EXAMPLES

       See the example "cbex01".

ACCESS

       To use the Bivar Fortran or C routines, load the NCAR Graphics libraries ncarg, ncarg_gks,
       and ncarg_c, preferably in that order.

MESSAGES

       When error conditions are detected, the support routine SETER is called. By default, SETER
       writes a message to the standard error file (as defined by I1MACH(4)) and then terminates
       execution.  It is possible to put SETER into recovery mode and regain control after a
       recoverable error (which includes all of the possible errors).

       The possible error messages are listed below.  All errors are recoverable in the sense
       that a user program which has called ENTSR to set recovery mode will get control back
       after one of these errors occurs.

       IDBVIP (BIVAR) - UNCLEARED PRIOR ERROR

       IDBVIP (BIVAR) - INPUT VARIABLE MD IS OUT OF RANGE

       IDBVIP (BIVAR) - INPUT VARIABLE NDP IS OUT OF RANGE

       IDBVIP (BIVAR) - INPUT VARIABLE NIP IS OUT OF RANGE

       IDBVIP (BIVAR) - MD = 2 OR 3 BUT NDP WAS CHANGED SINCE LAST CALL

       IDBVIP (BIVAR) - MD = 3 BUT ITY WAS CHANGED SINCE LAST CALL

       IDBVIP (BIVAR) - MD = 3 BUT NIP WAS CHANGED SINCE LAST CALL

       IDGETI (BIVAR) - UNCLEARED PRIOR ERROR

       IDGETR (BIVAR) - UNCLEARED PRIOR ERROR

       IDGETR (BIVAR) - INVALID KEYWORD: xxx

       IDGRID (BIVAR) - INTERNAL ERROR - SEE CONSULTANT

       IDPLTR (BIVAR) - UNCLEARED PRIOR ERROR

       IDSETI (BIVAR) - UNCLEARED PRIOR ERROR

       IDSETR (BIVAR) - UNCLEARED PRIOR ERROR

       IDSETR (BIVAR) - INVALID KEYWORD: xxx

       IDSFFT (BIVAR) - UNCLEARED PRIOR ERROR

       IDSFFT (BIVAR) - INPUT VARIABLE MD IS OUT OF RANGE

       IDSFFT (BIVAR) - INPUT VARIABLE NDP IS OUT OF RANGE

       IDSFFT (BIVAR) - INPUT VARIABLE NXI OR NYI IS OUT OF RANGE

       IDSFFT (BIVAR) - INPUT VARIABLE NZI IS LESS THAN NXI

       IDSFFT (BIVAR) - MD = 2 OR 3 BUT NDP WAS CHANGED SINCE LAST CALL

       IDSFFT (BIVAR) - MD = 3 BUT ITY WAS CHANGED SINCE LAST CALL

       IDSFFT (BIVAR) - MD = 3 BUT NXI WAS CHANGED SINCE LAST CALL

       IDSFFT (BIVAR) - MD = 3 BUT NYI WAS CHANGED SINCE LAST CALL

       IDTANG (BIVAR) - INPUT PARAMETER NDP OUT OF RANGE

       IDTANG (BIVAR) - TWO OF THE INPUT DATA POINTS ARE IDENTICAL

       IDTANG (BIVAR) - ALL COLLINEAR DATA POINTS

SEE ALSO

       Online: bivar_params, idbvip, idsfft, idpltr, idgeti, idgetr, idseti, idsetr, ncarg_cbind

       Hardcopy: NCAR Graphics Contouring and Mapping Tutorial; NCAR Graphics Fundamentals, UNIX
       Version

ACKNOWLEDGMENTS

       Bivar was written by Hiroshi Akima in August 1975 and rewritten by him in late 1976.  In
       1989, a new version of Bivar, incorporating changes described in a Rocky Mountain Journal
       of Mathematics was obtained from Dr. Akima, and included in NCAR Graphics with his
       permission.  In 1995, Dave Kennison incorporated the capability of doing linear
       interpolation and a different kind of triangulation, put in a parameter access interface,
       and wrote a routine to allow the triangulation to be plotted.

COPYRIGHT

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