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### SPRSAX

SPRSAX

The SPRSAX function takes a row-indexed sparse array created by the SPRSIN function and multiplies it by an n-element vector to its right.

## Examples

`; Begin by creating an array A:A = [[ 5.0,  0.0, 0.0], \$     [ 3.0, -2.0, 0.0], \$     [ 4.0, -1.0, 0.0]]; Define the right-hand vector:X = [1.0, 2.0, -1.0]; Convert to sparse format, then multiply by X:result = SPRSAX(SPRSIN(A),X); Print the result:PRINT, result`

IDL prints:

`5.00000     -1.00000      2.00000`

## Syntax

Result = SPRSAX( A, X [, /DOUBLE] )

## Return Value

Returns a n-element vector.

## Arguments

### A

A row-indexed sparse array created by the SPRSIN function.

Note: If SPRSAX is complex then only the real part is used for the computation.

### X

An n-element right hand vector.

## Keywords

### DOUBLE

Set this keyword to force the computation to be done in double-precision arithmetic.

## Version History

 4 Introduced

## Resources and References

SPRSAX is based on the routine sprsax described in section 2.7 of Numerical Recipes in C: The Art of Scientific Computing (Second Edition), published by Cambridge University Press, and is used by permission.

## See Also

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