MATLAB Application Program Interface Reference

Get the number of rows

#include "matrix.h"
int mxGetM(const mxArray *array_ptr);

Arguments

array_ptr

Pointer to an array.

Returns

The number of rows in the mxArray to which array_ptr points.

Description

mxGetM returns the number of rows in the specified array. The term "rows" always means the first dimension of the array no matter how many dimensions the array has. For example, if array_ptr points to a four-dimensional array having dimensions 8-by-9-by-5-by-3, then mxGetM returns 8.

Examples

Consider a MEX-file that accepts two input mxArray arguments. Both mxArray arguments must have the same number of rows in order for the calculation to work.

void
mexFunction(int nlhs,mxArray *plhs[],int nrhs,const mxArray 
*prhs[])
{
 int rows;

    rows = mxGetM(prhs[0]);
    if (rows != 1)
      mexErrMsgTxt("First input array must be a vector."); 
    else
   ...

For an additional example, see mxGetM.c in the mx subdirectory of the examples directory.