User`s manual

Examples of C MEX-Files

2-29

This example determines the position of all nonzero elements in the matrix.

Running the MEX-file on this matrix produces

nz = findnz(matrix)

nz =

1 1

4 1

5 1

2 2

3 2

5 2

1 3

2 3

3 3

4 3

5 3

2 4

3 4

4 4

Handling Sparse Arrays

The MATLAB API provides a set of functions that allow you to create and

manipulate sparse arrays from within your MEX-files. These API routines

access and manipulate

ir and jc, two of the parameters associated with sparse

arrays. For more information on how MATLAB stores sparse arrays, refer to

the section, “The MATLAB Array” on page 1-6.

This example illustrates how to populate a sparse matrix.

/*==============================================================

* fulltosparse.c

* This example demonstrates how to populate a sparse

* matrix. For the purpose of this example, you must pass in a

* non-sparse 2-dimensional argument of type double.

* Comment: You might want to modify this MEX-file so that you can

* use it to read large sparse data sets into MATLAB.

* This is a MEX-file for MATLAB.