[R] Plotting with Statistics::R, Perl/R

[Tim Churches]

Joe Conway wrote:

> Dirk Eddelbuettel wrote:
>
>> On Fri, Jan 21, 2005 at 06:06:45PM -0800, Leah Barrera wrote:
>>
>>> I am trying to plot in R from a perl script using the Statistics::R
>>>  package as my bridge.  The following are the conditions:
>>>
>>> 0. I am running from a Linux server.
>>>
>> Plotting certain formats requires the X11 server to be present as the
>> font metrics for those formats can be supplied only the X11 server.
>> Other drivers don;t the font metrics from X11 -- I think pdf is a
>> good counterexample. When you run in 'batch' via a Perl script, you
>> don't have the X11 server -- even though it may be on the machine and
>> running, it is not associated with the particular session running
>> your Perl job.  There are two common fixes:
>>
>> a) if you must have png() as a format, you can start a virtual X11
>> server with the xvfb server -- this is a bit involved, but doable;
>
>
> Attached is an init script I use to start up xvfb on Linux.
>
> HTH,
>
> Joe
>
>------------------------------------------------------------------------
>
>#!/bin/bash
>#
># syslog        Starts Xvfb.
>#
>#
># chkconfig: 2345 12 88
># description: Xvfb is a facility that applications requiring an X frame buffer \
># can use in place of actually running X on the server
>
># Source function library.
>. /etc/init.d/functions
>
>[ -f /usr/X11R6/bin/Xvfb ] || exit 0
>
>XVFB="/usr/X11R6/bin/Xvfb :5 -screen 0 1024x768x16"
>
>RETVAL=0
>
>umask 077
>
>start() {
>        echo -n $"Starting Xvfb: "
>        $XVFB&
>        RETVAL=$?
>        echo_success
>        echo
>        [ $RETVAL = 0 ] && touch /var/lock/subsys/Xvfb
>        return $RETVAL
>}
>stop() {
>        echo -n $"Shutting down Xvfb: "
>        killproc Xvfb
>        RETVAL=$?
>        echo
>        [ $RETVAL = 0 ] && rm -f /var/lock/subsys/Xvfb
>        return $RETVAL
>}
>restart() {
>        stop
>        start
>}
>
>case "$1" in
>  start)
>        start
>        ;;
>  stop)
>        stop
>        ;;
>  restart|reload)
>        restart
>        ;;
>  condrestart)
>        [ -f /var/lock/subsys/Xvfb ] && restart || :
>        ;;
>  *)
>        echo $"Usage: $0 {start|stop|restart|condrestart}"
>        exit 1
>esac
>
>exit $RETVAL
>  
>
Hmm, the only problem with that is that, if I am not mistaken, you are 
starting Xvfb without any authentication, and I am told by people who 
know about such things that in the context of an Internet-accessible Web 
server, having an X server accepting unauthenticated connections is not 
a good idea. In other, less hostile environments, it might be OK. Maybe 
such concerns are unreasonable paranoia, but my motto is better safe 
than sorry when it comes to Internet-facing servers. I think there are 
also other switches you can pass to Xvfb to stop it listening on various 
TCP/IP ports etc.

Tim C