Offset from first element to desired element
#include "matrix.h" mwIndex mxCalcSingleSubscript(const mxArray *pm, mwSize nsubs, mwIndex *subs);
#include "fintrf.h" mwIndex mxCalcSingleSubscript(pm, nsubs, subs) mwPointer pm mwSize nsubs mwIndex subs
pmPointer to an mxArray
nsubsNumber of elements in the subs array. Typically, you
set nsubs equal to the number of dimensions in the
mxArray that pm points to.
An array of integers. Each value in the array specifies that dimension's
subscript. In C syntax, the value in subs[0] specifies
the row subscript, and the value in subs[1] specifies the
column subscript. Use zero-based indexing for subscripts. For example, to
express the starting element of a two-dimensional mxArray
in subs, set subs[0] to
0 and subs[1] to
0.
In Fortran syntax, the value in subs(1) specifies the
row subscript, and the value in subs(2) specifies the
column subscript. Use 1-based indexing for subscripts. For example, to
express the starting element of a two-dimensional mxArray
in subs, set subs(1) to
1 and subs(2) to
1.
The number of elements, or index, between the start of the
mxArray and the specified subscript. This number is the linear
index equivalent of the subscripts. Many Matrix Library routines (for example,
mxGetField) require an index as an argument.
If subs describes the starting element of an
mxArray, mxCalcSingleSubscript returns 0. If
subs describes the final element of an
mxArray, mxCalcSingleSubscript returns
N-1 (where N is the total number of
elements).
Call mxCalcSingleSubscript to determine how many elements there
are between the beginning of the mxArray and a given element of that
mxArray. The function converts subscripts to linear
indices.
For example, given a subscript like (5,7),
mxCalcSingleSubscript returns the distance from the first
element of the array to the (5,7) element. Remember that the
mxArray data type internally represents all data elements in a
one-dimensional array no matter how many dimensions the MATLAB®
mxArray appears to have. For examples showing the internal
representation, see Data Storage.
Avoid using mxCalcSingleSubscript to traverse the elements of an
array. In C, it is more efficient to find the starting address of the array and then use
pointer autoincrementing to access successive elements. For example, to find the
starting address of a numerical array, call one of the typed data access functions, for
example, mxGetDoubles or
mxGetComplexDoubles.