AS R - Average images - find & save variance, better

PURPOSE

Adds 2 or more files, computing several measures of variance (per point, total, etc.). The sum and the variance images are stored in separate output files. The command works for, 2D, 3D, real or complex data.

SEE ALSO

AS	[Average images - find variance]
AS AD	[Average images - add to an existing average]
AS F	[Average images - find statistics & Q factor map ||]

USAGE

.OPERATION: AS R

.INPUT FILE NAME TEMPLATE (E.G. PIC****): PIC***
[Enter name of image series to be added. Astericks in the template will be replaced by numbers solicted next.]

.ENTER SELECTION DOC. FILE NAME OR LIST OF FILE NUMBERS: 1-10,12,15-17 1-8
[Enter numbers of files within the series to be added. The file numbers can also be read from a selection document file where file numbers are contained in the first register (not the keys!).]

.ALL, ODD-EVEN (A/O): O
['A' - all images will be added, 'O' - two sub-averages will be calculated: one for odd-numbered images and one for even numbered images. For 'O' option the next two questions will appear twice.]

.AVERAGE FILE: AVG001
[Enter name of output file receiving average.]

.VARIANCE FILE: VAR001
[Enter name of output file receiving variance map.]

The following values are then printed out:

 
           Number of images 
           Number of elements 
           Total variance             Total std. deviation 
           Variance. per point        Std. deviation per point 
           Average offset = 0.0 
           Variance of average image 

NOTES

1. This version of 'AS' does not subtract the average from each image during the calculation of global average and variance. Thus, the statistics calculated are 'Real' and the average offset is always zero. Command 'AS' results in the variance estimator which is usually far 'too optimistic' - the variance obtained is too small and cannot be used for statistical tests.

2. Merged with operation "AS DC" July 1999

SUBROUTINES

ADDS

CALLER

UTIL2