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.

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.

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.

X

An n-element right hand vector.

Keywords

DOUBLE

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

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 

Version History

Introduced: 4.0

See Also

FULSTR, LINBCG, SPRSAB, SPRSIN, SPRSTP, READ_SPR, WRITE_SPR