# ncl_bivar man page

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.