


XFORM(UCL)        MISC. REFERENCE MANUAL PAGES         XFORM(UCL)



NAME
     xform -- perform transformations on PRW text data stream

SYNOPSIS
     xform (-t) (-s) <pvin.txt >pvout.txt
     xform  (-l  numdisc)  (-p   numprinc)   statfile   <pvin.txt
     >pvout.txt

DESCRIPTION
     xform is a program to process a text stream of pattern  vec-
     tor  data  in the vector labelled format accepted by gendat.
     It operates in two modes: external  files  (linear  discrim-
     inants  and  principle components) and one based on internal
     transformations (convolution and auto-correlation).

  EXTERNAL TRANSFORMATIONS
     The vecstat program can be used to analyse a  complete  data
     set  and  generate either a set of linear discriminant func-
     tions or a set of principle components.  vecstat stores  the
     calculated factors in an external statistics file that xform
     can read in.  The options -l and -p read in the given number
     of  factors  to generate transformed output vectors.  If the
     number of factors requested is zero, then the maximum number
     available in the file are used.

  INTERNAL TRANSFORMATIONS
     If the input pattern is R rows by  C  columns,  the  program
     performs  an autocorrelation in the row direction and a con-
     volution in the column direction to attempt to remove  posi-
     tion  dependent  and  long-distance  correlations in the row
     direction.  The result is a matrix of R by  (2*C-1)  values,
     which  is  output  in the default operation.  An option (-t)
     allows for the output of the  most  significant  portion  of
     this  matrix, such that the total number of values output is
     the same as the number input, i.e. R*C; this matrix is  for-
     matted as 1 row by R*C columns.

OPTIONS
     -I         Identify program name and version number.

     -t         (Convolution/Auto-correlation)Truncate
                transformed data to same size as input pattern.

     -s         (Convolution/Auto-correlation)Scale  output  data
                so that all values in range -1..1.

     -lnumdisc  Apply discriminants found  in  supplied  file  to
                generate  new  vectors.   The  number of discrim-
                inants to use is supplied in numdisc.  If numdisc
                is zero, then all those found are used.

     -pnumprinc Apply principle components found in supplied file



Sun Release 4.1         Last change: PRW1                       1






XFORM(UCL)        MISC. REFERENCE MANUAL PAGES         XFORM(UCL)



                to  generate  new  vectors.   The  number of com-
                ponents to  use  is  supplied  in  numprinc.   If
                numprinc is zero then all those found are used.

VERSION/AUTHOR
     1.1  Mark Huckvale

SEE ALSO
     gendat, runchop, xpose, vecstat

BUGS
SOURCE
     /users/mark/sfs/man/../prw/util.src/xform.c










































Sun Release 4.1         Last change: PRW1                       2



