NAME

PDL::IO::Misc - misc IO routines for PDL


DESCRIPTION

A mixture of basic I/O functionality


SYNOPSIS

 use PDL::IO::Misc;


FUNCTIONS


rfits()

Simple piddle FITS reader.

  $pdl = rfits('file.fits');

Suffix magic:

  # Automatically uncompress via gunzip pipe
  $pdl = rfits('file.fits.gz');
  # Automatically uncompress via uncompress pipe 
  $pdl = rfits('file.fits.Z');  

FITS Headers stored in piddle and can be retrived with $a->gethdr.

This header is a reference to a hash where the hash keys are the keywords in the FITS header. It is important to note that for strings, the surrounding quotes are kept to ensure that strings that look like numbers are kept as strings. This is also of importance if you create your own header information and you want the value to be printed out as a string.

Comments in headers are stored as $$h{COMMENT}{<Keyword>} where $h is the header retrieved with $a->gethdr. History entries in the header are stored as $$h{HISTORY}, which is an anonymous array for each HISTORY entry in the header.


wfits()

Simple piddle FITS writer

  wfits $pdl, 'filename.fits', [$BITPIX];
  $pdl->wfits('foo.fits',-32);

Suffix magic:

  # Automatically compress through pipe to gzip
  wfits $pdl, 'filename.fits.gz';
  # Automatically compress through pipe to compress 
  wfits $pdl, 'filename.fits.Z';  

$BITPIX is optional and coerces the output format.


rcols()

Read ASCII whitespaced cols from file into piddles efficiently (also see rgrep()).

There are two calling conventions - the old version, where a pattern can be specified after the filename/handle, and the new version where options are given as as hash reference. This reference can be given as either the second or last argument.

The default behaviour is to ignore lines beginning with a # character and lines that only consist of whitespace. Options exist to only read from lines that match, or do not match, supplied patterns.

Options:

  EXCLUDE or IGNORE
     - ignore lines matching this pattern (default '/^#/').
  INCLUDE or KEEP
     - only use lines which match this pattern (default '').
  LINES   
     - which line numbers to use. Line numbers start at 0 and the syntax 
       is 'a:b:c' to use every c'th matching line between a and b
       (default '').
  PERLCOLS
     - an array of column numbers which are to be read into perl arrays
       rather than piddles. References to these arrays are returned after
       the requested piddles.

Can take file name or *HANDLE, and if no columns are specified, all are assumed.

  Usage:
    ($x,$y,...) = rcols( *HANDLE|"filename", { EXCLUDE => '/^!/' }, 
                         $col1, $col2, ... )
    ($x,$y,...) = rcols( *HANDLE|"filename", $col1, $col2, ..., 
                         { EXCLUDE => '/^!/' } )
    ($x,$y,...) = rcols( *HANDLE|"filename", "/foo/", $col1, $col2, ... )
 
e.g.,

  $x         = PDL->rcols 'file1';
  ($x,$y)    = rcols *STDOUT;

  # read in lines containing the string foo, where the first
  # example also ignores lines that with a # character.
  ($x,$y,$z) = rcols 'file2', 0,4,5, { INCLUDE => '/foo/' };
  ($x,$y,$z) = rcols 'file2', 0,4,5, { INCLUDE => '/foo/', EXCLUDE => '' };

  # ignore the first 27 lines of the file
  ($x,$y) = rcols 'file3', { LINES => '27:-1' }
  ($x,$y) = rcols 'file3', { LINES => '27:' }

  # read in the first column as a perl array and the next two as piddles
  ($x,$y,$name) = rcols 'file4', 1, 2, { PERLCOLS => [ 0 ] };
  printf "Number of names read in = %d\n", 1 + $#$name;

Notes:

1. Quotes are required on patterns.

2. Columns are separated by whitespace by default, use $PDL::IO::Misc::colsep to specify an alternate separator.

3. To remove a particular check set its value to ''.

4. For PDL-2.003, the meaning of the 'c' value in the LINES option has changed: it now only counts matching lines rather than all lines as in previous versions of PDL.


wcols()

Write ASCII whitespaced cols into file from piddles efficiently.

If no columns are specified all are assumed. Will optionally only process lines matching a pattern. Can take file name or *HANDLE, e.g.

 Usage: wcols $piddle1, $piddle2,..., *HANDLE|"outfile";

e.g.,

  wcols $x, $y+2, 'foo.dat';
  wcols $x, $y+2, *STDERR;
  wcols $x, $y+2, '|wc';
  wcols $a,$b,$c; # Orthogonal version of 'print $a,$b,$c' :-)

  wcols "%10.3f", $a,$b; # Formatted
  wcols "%10.3f %10.5g", $a,$b; # Individual column formatting

Note: columns are separated by whitespace by default, use $PDL::IO::Misc::colsep to specify an alternate separator.

If no file/filehandle is given defaults to STDOUT


rgrep()

Read columns into piddles using full regexp pattern matching.

Usage

 ($x,$y,...) = rgrep(sub, *HANDLE|"filename")

e.g.

 ($a,$b) = rgrep {/Foo (.*) Bar (.*) Mumble/} $file;

i.e. the vectors $a and $b get the progressive values of $1, $2 etc.


rdsa()

Read a FIGARO/NDF format file.

Requires non-PDL DSA module. Contact Frossie (frossie@jach.hawaii.edu) Usage:

 ([$xaxis],$data) = rdsa($file)

 $a = rdsa 'file.sdf'

Not yet tested with PDL-1.9X versions


isbigendian()

Determine endianness of machine - returns 0 or 1 accordingly


rasc()

Simple function to slurp in ASCII numbers quite quickly, although error handling is marginal (to nonexistent).

  $pdl->rasc("filename" [,$noElements]);
      Where:
        filename is the name of the ASCII file to read
        $noElements is the optional number of elements in the file to read.
             (If not present, all of the file will be read to fill up $pdl)

  #  (test.num is an ascii file with 20 numbers. One number per line.)
  $in = PDL->null;
  $num = 20;
  $in->rasc('test.num',20);
  $imm = zeroes(float,20,2);
  $imm->rasc('test.num');


rcube

Read list of files directly into a large data cube (for efficiency)

 $cube = rcube \&reader_function, @files;

 $cube = rcube \&rfits, glob("*.fits");

This IO function allows direct reading of files into a large data cube, Obviously one could use cat() but this is more memory efficient.

The reading function (e.g. rfits, readfraw) (passed as a reference) and files are the arguments.

The cube is created as the same X,Y dims and datatype as the first image specified. The Z dim is simply the number of images.


_rasc

  Signature: ([o] nums(n); int num => n; char* fd)

Internal Function used by rasc.


bswap2

  Signature: ([o]x(); )

Swaps pairs of bytes in argument x()


bswap4

  Signature: ([o]x(); )

Swaps quads of bytes in argument x()


bswap8

  Signature: ([o]x(); )

Swaps octets of bytes in argument x()


AUTHOR

Copyright (C) Karl Glazebrook 1997. All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the copyright notice should be included in the file.