IDL Reference Guide: Procedures and Functions

LA_INVERT

The LA_INVERT function uses LU decomposition to compute the inverse of a square array.

LA_INVERT is based on the following LAPACK routines:

For more details, see Anderson et al., LAPACK Users' Guide, 3rd ed., SIAM, 1999.

Syntax

Result = LA_INVERT( A [, /DOUBLE] [, STATUS=variable] )

Return Value

The result is an array of the same dimensions as the input array.

Arguments

A

The n-by-n array to be inverted.

Keywords

DOUBLE

Set this keyword to use double-precision for computations and to return a double-precision (real or complex) result. Set DOUBLE = 0 to use single-precision for computations and to return a single-precision (real or complex) result. The default is /DOUBLE if A is double precision, otherwise the default is DOUBLE = 0.

STATUS

Set this keyword to a named variable that will contain the status of the computation. Possible values are:

Examples

The following program computes the inverse of a square array:

PRO ExLA_INVERT  
; Create a square array.  
array =[[1d, 2, 1], $  
     [4, 10, 15], $  
     [3, 7, 1]]  
; Compute the inverse and check the error.  
ainv = LA_INVERT(array)  
PRINT, 'LA_INVERT Identity Matrix:'  
PRINT, ainv ## array  
END  

When this program is compiled and run, IDL prints:

A_INVERT Identity Matrix:  
1.0000000   1.7763568e-015  6.6613381e-016 
0.00000000  1.0000000       1.2212453e-015 
0.00000000  0.00000000      1.0000000