Main Content

mxCalcSingleSubscript (Fortran)

Offset from first element to desired element

Fortran Syntax

#include "fintrf.h"
mwIndex mxCalcSingleSubscript(pm, nsubs, subs)
mwPointer pm
mwSize nsubs
mwIndex subs

Description

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.

Input Arguments

expand all

Pointer to an mxArray array, specified as mwPointer.

Number of elements in the subs array, specified as mwSize. Typically, you set nsubs equal to the number of dimensions in the mxArray that pm points to.

Array of subscripts, specified as mwIndex. Each value in the array specifies that dimension's subscript. 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.

Returns

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).

Introduced before R2006a