From bug-request at octave dot org Wed Apr  5 14:43:03 2006
Subject: Re: Plot should be able to handle empty vector inputs
From: Quentin Spencer <qspencer at ieee dot org>
To: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
CC: octave bug mailing list <bug at octave dot org>
Date: Wed, 05 Apr 2006 14:34:31 -0500

John W. Eaton wrote:
> On  5-Apr-2006, Quentin Spencer wrote:
>
> | In Matlab, it is possible to call the plot function with empty data.
> | This is an error
> |  >> plot([])
> | ??? Error using ==> plot
> | Vectors must be the same lengths.
> | 
> | However, this is acceptable.
> |  >> plot([],[])
> | 
> | 
> | In octave, I get the following error:
> | oct 1> plot([],[])
> | error: __plt2__: invalid data for plotting
> | error: evaluating if command near line 48, column 3
> | error: called from `__plt2__' in file 
> | `/usr/share/octave/2.9.4/m/plot/__plt2__.m'
> | error: evaluating if command near line 58, column 4
> | error: evaluating if command near line 56, column 2
> | error: evaluating if command near line 55, column 7
> | error: evaluating while command near line 44, column 5
> | error: evaluating if command near line 34, column 3
> | error: called from `__plt__' in file 
> | `/usr/share/octave/2.9.4/m/plot/__plt__.m'
> | error: called from `plot' in file `/usr/share/octave/2.9.4/m/plot/plot.m'
> | 
> | Supporting this behavior is useful because I have a situation where I'm 
> | plotting several vectors, and one pair of them may be empty, but I don't 
> | know in advance without extra code to check for it. As you can see, this 
> | is version 2.9.4, but looking at CVS, it looks like this hasn't changed 
> | since then.
>
> kHow about the following change.  I think it does what you want, but
> I've not done a lot of testing.
>
> | I might be able to write a patch for this, but I don't have 
> | time right now--maybe later if I'm the first one to get to it.
>
> Oops, sorry.  Well, instead of a patch, can you at do some testing of
> the one below?
>   

I just tried it in the application that was breaking for me before and 
it worked exactly as expected. Thanks.

-Quentin



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