NAME

       PDL::IO - An overview of the modules in the PDL::IO namespace.

SYNOPSIS

        # At your system shell, type:
        perldoc PDL::IO

DESCRIPTION

       PDL contains many modules for displaying, loading, and saving data.

       •   Perlish or Text-Based

           A   few   IO   modules   provide   Perl-inspired   capabilities.    These   are  PDL::IO::Dumper  and
           PDL::IO::Storable.  PDL::IO::Misc provides simpler routines for dealing with delimited files,  though
           its capabilities are limited to tabular or at most 3-d data sets.

       •   Raw Format

           PDL  has  two  modules  that  store  their data in a raw binary format; they are PDL::IO::FastRaw and
           PDL::IO::FlexRaw.  They are fast but the files they produce will not  be  readable  across  different
           architectures.  These two modules are so similar that they could probably be combined.

       •   Data Browsing

           At the moment, only PDL::IO::Browser provides data browsing functionality.

       •   Image Handling

           PDL  has  a  handful  of  modules  that  will  load  images  into  ndarrays  for  you.   They include
           PDL::IO::Dicom, PDL::IO::FITS, PDL::IO::GD, PDL::IO::Pic, and PDL::IO::Pnm.   However,  PDL::IO::FITS
           should also be considered something of a general data format.

       •   Disk Caching

           Both  PDL::IO::FastRaw  and PDL::IO::FlexRaw provide for direct ndarray-to-disk mapping, but they use
           PDL's underlying mmap functionality to do it, and that doesn't work for Windows.  However,  users  of
           all  operating  systems  can  still  use  PDL::DiskCache,  which  can  use  any desired IO read/write
           functionality (though you may have to write a small wrapper function).

       •   General Data Storage Formats

           PDL has a number of modules that interface general data storage libraries.  They include PDL::IO::HDF
           and PDL::IO::NDF (the latter is now a separate CPAN module).  There is a PDL::IO::IDL, though at  the
           moment  it  is  not distributed with PDL.  PDL::IO::FITS is something of a general data format, since
           ndarray data can be stored to a FITS file without loss.  PDL::IO::FlexRaw and  PDL::IO::FastRaw  read
           and write data identical C's low-level "write" function and PDL::IO::FlexRaw can work with FORTRAN 77
           UNFORMATTED files.  FlexRaw and Storable provide general data storage capabilities.  Finally, PDL can
           read Grib (weather-data) files using the CPAN module PDL::IO::Grib.

       •   Making Movies

           You can make an MPEG animation using PDL::IO::Pic's wmpeg function.

       Here's a brief summary of all of the modules, in alphabetical order.

   PDL::DiskCache
       The  DiskCache module allows you to tie a Perl array to a collection of files on your disk, which will be
       loaded into and out of memory as ndarrays.  Although the module defaults to working with FITS  files,  it
       allows  you to specify your own reading and writing functions.  This allows you to vastly streamline your
       code by hiding the unnecessary details of loading and saving files.

       If you find yourself writing scripts to procss many data files, especially if that data processing is not
       necessarily in sequential order, you should consider using  PDL::DiskCache.   To  read  more,  check  the
       PDL::DiskCache documentation.

   PDL::IO::Browser
       The Browser module provides a text-based data browser for 2D data sets.

       It  uses  the  CURSES  library to do the scrolling, so if your operating system does not have the cureses
       library, you won't be able to install this on your machine.  (Note that the package containing the header
       files for the CURSES library may be called "libcurses" or possibly "libncurses".)

       To see if the module is installed on your machine (and to get more information  about  PDL::IO::Browser),
       follow this link or type at the system prompt:

        perldoc PDL::IO::Browser

       If  you  want  to  get more information about PDL::IO::Browser and it's not installed on your system, I'm
       afraid you'll  have  to  pick  out  the  pod  from  the  source  file,  which  can  be  found  online  at
       <https://github.com/PDLPorters/pdl/blob/master/IO/Browser/browser.pd>.

   PDL::IO::Dicom
       DICOM  is an image format, and this module allows you to read image files with the DICOM file format.  To
       read more, check the PDL::IO::Dicom documentation.

   PDL::IO::Dumper
       Provides functionality similar to Data::Dumper for ndarrays.  Data::Dumper stringifies a data  structure,
       creating  a  string  that  can  be  "eval"ed to reproduce the original data structure.  It's also usually
       suitable for printing, to visualize the structure.

       To  read  more,  check  the  PDL::IO::Dumper  documentation.   See  also  PDL::IO::Storable  for  a  more
       comprehensive structured data solution.

   PDL::IO::FastRaw
       Very simple module for quickly writing, reading, and memory-mapping ndarrays to/from disk.  It is fast to
       learn  and  fast to use, though you may be frustrated by its lack of options.  To quote from the original
       POD:

       "The binary files are in general NOT interchangeable between different  architectures  since  the  binary
       file is simply dumped from the memory region of the ndarray.  This is what makes the approach efficient."

       This creates two files for every ndarray saved - one that stores the raw data and another that stores the
       header  file,  which  indicates the dimensions of the data stored in the raw file.  Even if you save 1000
       different ndarrays with the exact same dimensions, you will still need to write out  a  header  file  for
       each one.  You cannot store multiple ndarrays in one file.

       Note that at the time of writing, memory-mapping is not possible on Windows.

       For more details, see PDL::IO::FastRaw.  For a more flexible raw IO module, see PDL::IO::FlexRaw.

   PDL::IO::FITS
       Allows  basic  reading  and  writing  of  FITS  files.   You  can read more about FITS formatted files at
       <http://fits.gsfc.nasa.gov/fits_intro.html> and  <http://en.wikipedia.org/wiki/FITS>.   It  is  an  image
       format commonly used in Astronomy.

       This  module  may  or  may  not  be  installed on your machine.  To get more information, check online at
       <http://pdl.perl.org/?docs=IO/FITS&title=PDL::IO::FITS>.  To see if the module  is  installed,  look  for
       PDL::IO::FITS on your machine by typing at the system prompt:

        perldoc PDL::IO::FITS

   PDL::IO::FlexRaw
       Somewhat  smarter module (compared to FastRaw) for reading, writing, and memory mapping ndarrays to disk.
       In addition to everything that FastRaw can do, FlexRaw can also store multiple ndarrays in a single file,
       take user-specified headers (so you can use one header  file  for  multiple  files  that  have  identical
       structure),  and  read  compressed data.  However, FlexRaw cannot memory-map compressed data, and just as
       with FastRaw, the format will not work across multiple architectures.

       FlexRaw and FastRaw produce  identical  raw  files  and  have  essentially  identical  performance.   Use
       whichever  module  seems to be more comfortable.  I would generally recommend using FlexRaw over FastRaw,
       but the differences are minor for most uses.

       Note that at the time of writing, memory-mapping is not possible on Windows.

       For more details on FlexRaw, see PDL::IO::FlexRaw.

   PDL::IO::GD
       GD is a library for reading, creating, and writing bitmapped images, written in C.   You  can  read  more
       about the C-library here: <http://www.libgd.org/>.

       In  addition  to  reading and writing .png and .jpeg files, GD allows you to modify the bitmap by drawing
       rectangles, adding text, and probably much more.  The documentation can  be  found  here.   As  such,  it
       should probably be not only considered an IO module, but a Graphics module as well.

       This module provides PDL bindings for the GD library, which ought not be confused with the Perl bindings.
       The  perl  bindings  were  developed independently and can be found at GD, if you have Perl's GD bindings
       installed.

   PDL::IO::Grib
       A CPAN module last updated in 2000 that allows you to read Grib files.  GRIB is a  data  format  commonly
       used  in  meteorology.   In  the  off-chance  that you have it installed, you should read PDL::IO::Grib's
       documentation.

   PDL::IO::HDF, PDL::IO::HDF5
       Provides an interface to HDF4 and HDF5 file formats, which  are  kinda  like  cross-platform  binary  XML
       files.  HDF stands for Heierarchicl Data Format.  HDF was originally developed at the NCSA.  To read more
       about  HDF,  see  <http://www.hdfgroup.org/>.   Note that HDF5 is not presently distributed with PDL, and
       neither HDF4 nor HDF5 will be installed unless you have the associated C  libraries  that  these  modules
       interface.   Also  note  that  the HDF5 library on CPAN is rather old and somebody from HDF contacted the
       mailing list in the Fall of 2009 to develop new and better HDF5 bindings for Perl.

       You should look into the PDL::IO::HDF (4) documentation or PDL::IO::HDF5  documentation,  depending  upon
       which module you have installed.

   PDL::IO::IDL
       Once  upon  a time, PDL had a module for reading IDL data files.  Unfortunately, it cannot be distributed
       because the original author, Craig DeForest, signed the IDL license agreement and was unable to negotiate
       the administrative hurdles to get it published.  However, it can be found in Sourceforge's CVS attic, and
       any PDL user who has not signed IDL's license agreement can fix it up and resubmit it.

   PDL::IO::Misc
       Provides mostly text-based IO routines.  Data input and output is restricted mostly to tabular (i.e. two-
       dimensional) data sets, though limited support is provided for 3d data sets.

       Alternative text-based modules support higher dimensions, such as PDL::IO::Dumper and  PDL::IO::Storable.
       Check the PDL::IO::Misc documentation for more details.

   PDL::IO::NDF
       Starlink developed a file format for N-Dimensional data Files, which it cleverly dubbed NDF.  If you work
       with these files, you're in luck!  Check the PDL::IO::NDF documentation for more details.

   PDL::IO::Pic
       Provides  reading/writing  of  images  to/from ndarrays, as well as creating MPEG animations!  The module
       uses the netpbm library, so you will need that on your machine in order for this to work.  To read  more,
       see the PDL::IO::Pic documentation.  Also look into the next module, as well as PDL::IO::GD.

   PDL::IO::Pnm
       Provides  methods  for  reading  and writing pnm files (of which pbm is but one).  Check the PDL::IO::Pnm
       documentation for more details.  Also check out the previous module and PDL::IO::GD.

   PDL::IO::Storable
       Implements the relevant methods to be able to store and retrieve ndarrays via Storable.   True,  you  can
       use  many  methods to save a single ndarray.  In contrast, this module is particularly useful if you need
       to save a complex Perl structure that contain ndarrays, such  as  an  array  of  hashes,  each  of  which
       contains ndarrays.

       Check  the PDL::IO::Storable documentation for more details.  See also PDL::IO::Dumper for an alternative
       stringifier.

COPYRIGHT

       Copyright 2010 David Mertens (dcmertens.perl@gmail.com). You can distribute and/or modify  this  document
       under the same terms as the current Perl license.

       See: http://dev.perl.org/licenses/

perl v5.34.0                                       2022-02-08                                            IO(3pm)