mxGetIr (C and Fortran)

Sparse matrix IR array

C Syntax

#include "matrix.h"
mwIndex *mxGetIr(const mxArray *pm);

Fortran Syntax

#include "fintrf.h"
mwPointer mxGetIr(pm)
mwPointer pm

Arguments

pm

Pointer to a sparse mxArray

Returns

Pointer to the first element in the ir array, if successful, and NULL in C (0 in Fortran) otherwise. Possible causes of failure include:

• Specifying a full (nonsparse) mxArray.

• Specifying a value for pm that is NULL in C (0 in Fortran). This failure usually means that an earlier call to mxCreateSparse failed.

Description

Use mxGetIr to obtain the starting address of the ir array. The ir array is an array of integers. The length of ir is nzmax, the storage allocated for the sparse array, or nnz, the number of nonzero matrix elements. For example, if nzmax equals 100, then the ir array contains 100 integers.

Each value in an ir array indicates a row (offset by 1) at which a nonzero element can be found. (The jc array is an index that indirectly specifies a column where nonzero elements can be found.)

For details on the ir and jc arrays, see mxSetIr and mxSetJc.

Examples

To open an example, type:

edit([fullfile(matlabroot,"extern","examples","refbook","filename")]);

where filename is:

• fulltosparse.c

• fulltosparse.F

To open an example, type:

edit([fullfile(matlabroot,"extern","examples","mx","filename")]);

where filename is:

• mxsetdimensions.c

• mxsetnzmax.c

To open an example, type:

edit([fullfile(matlabroot,"extern","examples","mex","filename")]);

where filename is:

• explore.c