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LA_INVERT

Syntax | Return Value | Arguments | Keywords | Examples | Version History | See Also

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:

• 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.

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

Version History

See Also

INVERT , LA_LUDC