How to programmatically access the transformation matricies of the ICA .trans file

The Independent Components (IC) analysis is used to transform a set of mixed, random signals into components that are mutually independent for multispectral or hyperspectral datasets.  The ICA transform produces a transformation matrix of the forward and backward transformation coefficients that are stored in a '.trans' file.  The following example shows how you can access these matricies in the .trans file.  It uses a undocumented routine, transform_read, that may need to be restored in your ENVI session to use. 

Note: Undocumented routines are unsupported by Exelis VIS and may change in a future version without notice.

First, if you are using a fresh IDL session, you will need to enter ENVI batch mode and then you will need to restore the following file:

ENVI>envi_check_save, /transform

Then you can access the items of the undocumented routine:

ENVI> help, /routines, name='transform_read', /full

Compiled Procedures:

TRANSFORM_READ          name FLOATING FORWARD_MATRIX INVERSE_EXIST INVERSE_MATRIX IN_NB OUT_NBRESERVE

To access the matricies, use the following syntax:

ENVI>transform_read, 'c:\temp\test.trans',floating=floating, forward_matrix=f, inverse_matrix=I

ENVI> print, f
     0.046469395    -0.047097945     0.023922794    0.0024658149
     0.038924652    0.0036077139    -0.011178614  -0.00034785035
    -0.024674406     0.039495369    -0.046729316     0.017028710
     -0.10597201     0.061793592    0.0040064471   -0.0039881298

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MM: June 19, 2015