mxGetData (C)

Data elements in nonnumeric mxArray

mxGetData is not recommended for numeric arrays. Use typed, data-access functions instead. For more information, see Version History.

C Syntax

#include "matrix.h"
void *mxGetData(const mxArray *pm);

Description

Use mxGetData to get data elements for nonnumeric arrays only.

For numeric arrays, MathWorks recommends that you create MEX files and update existing MEX files to use the typed, data-access functions in the interleaved complex API. For more information, see:

• Typed Data Access in C MEX Files

• MATLAB Support for Interleaved Complex API in MEX Functions

• Upgrade MEX Files to Use Interleaved Complex API

• Example explore.c

To build the MEX file, call mex with the -R2018a option.

Input Arguments

pm — Pointer to nonnumeric MATLAB^® array

mxArray *

Pointer to a nonnumeric MATLAB array, specified as mxArray *.

Output Arguments

pa — Pointer to data array

void * | NULL

Pointer to the data array within an mxArray, specified as void *. Since void pointers point to a value that has no type, cast the return value to the pointer type that matches the type specified by pm. For information on mapping MATLAB types to their equivalent C types, see mxClassID.

If pm is NULL, then the function returns NULL.

Version History

Introduced before R2006a

R2018a: For complex numeric mxArray, casting mxGetData return value depends on build option

The mxGetData function returns a void pointer. Your code must declare a pointer type that matches the type specified by the mxArray input argument. Use mxClassID to choose the correct type. For complex numeric input, the correct type depends on the build option used to create the MEX file.

If you build the MEX file with the default release-specific option (-R2017b), then the function returns a pointer to the first element of the real-only values.

If you build the MEX file with the -R2018a option, then:

• When input argument pm points to a real MATLAB array, the function returns a pointer to the first element of the data.

• When pm is a complex array, the function returns a pointer to the first element of the interleaved real and imaginary values, not to the real-only values.