Using the C Math Library

Evaluating Arrays for Sparse Storage

To see if a MATLAB array is a good candidate for sparse format storage, determine the number of nonzero elements in an array, using the mlfNnz() routine. The following code fragment creates the same 12-by-12 identity matrix, shown in the example in Converting an Existing Matrix into Sparse Format, and then prints out the number of nonzero elements in the matrix.

mxArray *I = NULL;

/* Create the array */
mlfAssign(&I, mlfEye(mlfScalar(12),NULL));

/* Determine the number of nonzero elements */
mlfPrintMatrix(mlfNnz(I));

mxDestroyArray(I);

This code outputs the number of nonzero elements in the 12-by-12 identity matrix: 12.

Converting a Sparse Matrix to Full Matrix Format

Character Arrays