help on plot in octave

[Ben Abbott]

On Jun 19, 2009, at 8:11 PM, Jason Ding wrote:

>
> On Jun 19, 2009, at 6:31 PM, Jason Ding wrote:
>
>> Hi, All,
>>
>> I installed both gnuplot and Octave. Gnuplot and octave work well
>> separately.  When I tried to use the "plot" function in octave, I
>> got the following errors after seeing an empty figure window popping
>> up. Can anyone have the similar experience? Or what may cause this?
>>
>> Thanks, a lot.
>>
>>
>> if (exists("GPVAL_TERM")) print GPVAL_TERM; else print NaN
>>                    ^
>>         line 0: invalid expression
>>
>> error: Invalid call to strcat.  Correct usage is:
>>
>> -- Function File:  strcat (S1, S2, ...)
>
>
> Please include the OS your are using as well as the version of Octave
> and gnuplot.
>
> The first error, complaining of GPVAL_TERM, appears to be from
> gnuplot. The "strcat" error is from Octave (but is only occurring
> because of the 1st error).
>
> Assuming your Octave version is > 3.0 and your gnuplot is 4.2.2 or
> more recent, it is likely that you don't have a default terminal type
> set for gnuplot.
>
> You'll want to set the GNUTERM environment variable. For Linux it
> should be set to "x11" or "wxt". For Mac OSX it can be set to "x11" or
> "aqua". For Windows  (I think) it can be set to "windows" and if you
> have x11 installed, then "x11" should also work (I'm guessing as I
> haven't used windows in years).
>
> Ben
>
>
> Ben,
>
> Thanks for your reply. Here is  more info about OS, GNUplot and  
> octave.
> Terminal type is set to x11, gnuplot is 4.0 and octave is 3.2.0.
>
> Thanks,
> Jason
>
> OS:
>
> Linux version 2.6.18-92.el5 (mockbuild at builder10.centos.org) (gcc
> version 4.1.2 20071124 (Red Hat 4.1.2-42)) #1 SMP Tue Jun 10 18:51:06
> EDT 2008
>
> GNUPLOT:
>
>     Version 4.0 patchlevel 0
>        last modified Thu Apr 15 14:44:22 CEST 2004
>        System: Linux 2.6.18-92.el5
>
>        Copyright (C) 1986 - 1993, 1998, 2004
>        Thomas Williams, Colin Kelley and many others
>
>        This is gnuplot version 4.0.  Please refer to the documentation
>        for command syntax changes.  The old syntax will be accepted
>        throughout the 4.0 series, but all save files use the new
> syntax.
>
>        Type `help` to access the on-line reference manual.
>        The gnuplot FAQ is available from
>                http://www.gnuplot.info/faq/
>
>        Send comments and requests for help to
>                <gnuplot-info at lists.sourceforge.net>
>        Send bugs, suggestions and mods to
>                <gnuplot-bugs at lists.sourceforge.net>
>
>
> Terminal type set to 'x11'
>
>
> Octave:
>
> GNU Octave, version 3.2.0
> Copyright (C) 2009 John W. Eaton and others.
> This is free software; see the source code for copying conditions.
> There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or
> FITNESS FOR A PARTICULAR PURPOSE.  For details, type `warranty'.
>
> Octave was configured for "x86_64-unknown-linux-gnu".
>
> Additional information about Octave is available at
> http://www.octave.org.
>
> Please contribute if you find this software useful.
> For more information, visit http://www.octave.org/help-wanted.html
>
> Report bugs to <bug at octave.org> (but first, please read
> http://www.octave.org/bugs.html to learn how to write a helpful  
> report).
>
> For information about changes from previous versions, type `news'.
>
> octave:1>
>

It appears that the problem may be that you are running a rather old  
version of gnuplot.

Can you upgrade to a version more recent than 4.2.2 (the latest  
release if 4.2.5).

Ben