MATLAB Application Program Interface Reference Help Desk

mxGetJc

Purpose

Get the jc array of a sparse matrix

C Syntax

Arguments

array_ptr

Pointer to a sparse mxArray.

Returns

A pointer to the first element in the jc array, if successful; otherwise, returns NULL. The most likely cause of failure is specifying an array_ptr that points to a full (nonsparse) mxArray.

Description

Use mxGetJc to obtain the starting address of the jc array. The jc array is an integer array having n+1 elements where n is the number of columns in the sparse mxArray. The values in the jc array indirectly indicate columns containing nonzero elements. For a detailed explanation of the jc array, see mxSetJc.

Examples

Consider a MEX-file named SecndCol that displays the number of nonzero elements in the second column of an input mxArray:

In MATLAB, create a sparse mxArray and put four nontrivial elements in the second column:

Now call SecndCol, passing the sparse mxArray as an input argument:

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

See Also

mxGetIr, mxSetIr, mxSetJc



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