Boulder Laboratory for 3-Dimensional Electron Microscopy of Cells

SUBIMSTAT(1)							 SUBIMSTAT(1)

NAME
	subimstat - Subtracts one average image from another with a t-test

SYNOPSIS
	subimstat

DESCRIPTION

  SUBIMSTAT subtracts one average image from another and uses
  standard deviation or variance images to find the statistical
  significance of the difference at each pixel, as evaluated by a t-
  statistic.  It then sets to zero all differences that are less
  significant than the specified level of significance.  It can also
  output pixel values reflecting the level of significance rather than
  the difference.
  
  The average and standard deviation/variance images can be ones
  produced by by IMAVGSTAT or by other means.  When one starts the
  program, one designates a pair of A files (with average and S.D./
  variance images) and a pair of B files.  One can then subtract any
  section in B from any section in A; A and B may be the same pair of
  files.
  
  The user is responsible for keeping track of how many samples were
  used in making each average, and informing this program of those
  numbers.  The program needs these numbers to compute the t-statistic
  and evaluate its significance.
  
  Entries to the program:
  
  Average image file A
  Standard deviation or variance image file A
  Average image file B, or Return if same as file for A
  Standard deviation or variance image file B, or Return if same as
     file for A
  Output image file to store differences in
  
  0 if the files have standard deviations in them, or 1 if the files
     have variances

  Number of differences to compute
  
  For each difference, enter:

     Section # in file A, section # in file B

     Number of samples making up those averages in A and B

     Significance level for setting differences to zero.  Enter a
        probability value such as 0.05, 0.01, etc.  Differences less
        significant than this value will be set to zero.  Enter a
        negative value to have significant pixels values set to 
        the negative of the log of the probability, or to the positive
        log for negative differences.  For example, positive and
        negative differences with a P of 0.01 would be output as
        2 and -2, respectively.

HISTORY
  Written by David Mastronarde,  1/27/90
  4/23/90 - have program look up criterion t value.
  4/12/95 - use local subroutines for t-value