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NAME

UCS::R::Expect - Expect-based implementation of R backend

SYNOPSIS

  use UCS::R::Expect;
  ## exports Start(), Stop() and Exec() functions into current namespace
  ## as well as LoadVector() and DumpVector()

DESCRIPTION

This module should only be used implicitly through UCS::R, which loads the more efficient UCS::R::RSPerl implementation if available, and falls back on UCS::R::Expect otherwise.

LIMITATIONS

This module starts an R process in the background and communicates with it interactively through the Expect module. This approach has several disadvantages:

• Invoking R commands, waiting for output from the R backend, and parsing that output causes substantial overhead for R function invocations, allowing less than 1000 invocations per second even on a fast machine.
• The return value of a function call has to be printed by R, then the resulting output has to be parsed by Perl. This interfacing method is rather frail and currently supports only numeric vectors as return values.
• The interface is extremely inefficient for exchanging large amounts of data between Perl and R. It may hang if the input/output buffers used by Expect overflow. Use the LoadVector and DumpVector functions to pass large numeric vectors to R and back.

Because of these limitations, it is highly recommended that you install and use the RSPerl interface (available from http://www.omegahat.org/) on Unix platforms. When RSPerl has been installed with support for calling R from Perl, it will automatically be detected and configured for use by the UCS installation script. See doc/install.txt for more information and installation tips.

COPYRIGHT

Copyright (C) 2004-2005 Stefan Evert.

This software is provided AS IS and the author makes no warranty as to its use and performance. You may use the software, redistribute and modify it under the same terms as Perl itself.

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