mxSetIr (C and Fortran)
IR array of sparse array
C Syntax
#include "matrix.h" void mxSetIr(mxArray *pm, mwIndex *ir);
Fortran Syntax
#include "fintrf.h" subroutine mxSetIr(pm, ir) mwPointer pm, ir
Arguments
pm
Pointer to a sparse
mxArray
ir
Pointer to the
irarray. The
irarray must be sorted in column-major order.
Description
Use
mxSetIr to specify the
ir array of a
sparse
mxArray. The
ir array is an array of
integers; the length of the
ir array equals the value of
nzmax, the storage allocated for the sparse array, or
nnz, the number of nonzero matrix elements.
Each element in the
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. See
mxSetJc for more details on
jc.)
For example, suppose that you create a
7-by-
3
sparse
mxArray named
Sparrow containing six
nonzero elements by typing:
Sparrow = zeros(7,3); Sparrow(2,1) = 1; Sparrow(5,1) = 1; Sparrow(3,2) = 1; Sparrow(2,3) = 2; Sparrow(5,3) = 1; Sparrow(6,3) = 1; Sparrow = sparse(Sparrow);
The
pr array holds the real data for the sparse matrix, which in
Sparrow is the five 1s and the one 2. If there is any nonzero
imaginary data, then it is in a
pi array.
Notice how each element of the
ir array is always 1 less than the
row of the corresponding nonzero element. For instance, the first nonzero element is in
row 2; therefore, the first element in
ir is 1 (that is, 2 – 1). The
second nonzero element is in row 5; therefore, the second element in
ir is 4 (5 – 1).
The
ir array must be in column-major order. The
ir array must define the row positions in column 1 (if any)
first, then the row positions in column 2 (if any) second, and so on, through column N.
Within each column, row position 1 must appear before row position 2, and so on.
mxSetIr does not sort the
ir array for you;
you must specify an
ir array that is already sorted.
This function does not free any memory allocated for existing data that it displaces.
To free existing memory, call
mxFree on the pointer returned by
mxGetIr before you call
mxSetIr.
Examples
See these examples in
:
matlabroot/extern/examples/mx
See these examples in
:
matlabroot/extern/examples/mex
Version History
Introduced before R2006a