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:

Output Type	LAPACK Routine
Float	sgetrf, sgetri
Double	dgetrf, dgetri
Complex	cgetrf, cgetri
Double complex	zgetrf, zgetri

Examples

The following program computes the inverse of a square array:

  ; 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

When this program is compiled and run, IDL prints:

LA_INVERT Identity Matrix:

1.0000000   1.7763568e-015  6.6613381e-016 0.00000000  1.0000000       1.2212453e-015 0.00000000  0.00000000      1.0000000

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:

STATUS = 0: The computation was successful.
STATUS > 0: The array is singular and the inverse could not be computed. The STATUS value specifies which value along the diagonal (starting at one) is zero.

Note: If STATUS is not specified, any error messages will be output to the screen.

Version History

5.6	Introduced

Resources and References

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