MATLAB Application Program Interface Reference Help Desk

mxGetNzmax

Purpose

Get the number of elements in the ir, pr, and (if it exists) pi arrays

C Syntax

Arguments

array_ptr

Pointer to a sparse mxArray.

Returns

The number of elements allocated to hold nonzero entries in the specified sparse mxArray, on success. Returns an indeterminate value on error. The most likely cause of failure is that array_ptr points to a full (nonsparse) mxArray.

Description

Use mxGetNzmax to get the value of the nzmax field. The nzmax field holds an integer value that signifies the number of elements in the ir, pr, and, if it exists, the pi arrays. The value of nzmax is always greater than or equal to the number of nonzero elements in a sparse mxArray. In addition, the value of nzmax is always less than or equal to the number of rows times the number of columns.

As you adjust the number of nonzero elements in a sparse mxArray, MATLAB often adjusts the value of the nzmax field. MATLAB adjusts nzmax in order to reduce the number of costly reallocations and in order to optimize its use of heap space.

Examples

Consider a MEX-file named SparCnt that displays

In MATLAB, create a sparse mxArray named sparrow. Then, pass sparrow as an argument to SparCnt:

Adding one nonzero element to sparrow causes MATLAB to increase nzmax by 10

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

See Also

mxSetNzmax



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