Re: Strange result using plot

[Geordie McBain]

I think the problem is that there's some limit to the length of the
command line that Gnuplot will accept, and you've caused Octave to
exceed it.  One way to plot lots of line segments is to rejig the data
so that the line segments are all in two big arrays (of abscissae and
ordinates) with true data separated by NaNs; i.e. every third element of
each of the two columns is NaN.  Check out my qquiver function for
drawing arrow plots of plane vector fields:

http://www.aeromech.usyd.edu.au/~mcbain/AerodynamicsI/octave/qquiver.m

On Tue, 2007-02-20 at 16:42 +0100, José Luis García Pallero wrote:
> Hi,
> I'm plotting a geodetic network and the plot command backs a strange
> result. I must plot a lot of lines and I use the plot command in the
> form:
> 
> hold on;
> for i=1:rows
>     plot([xStart xEnd],[yStart yEnd],'g'); 
> end
> 
> When the loop arrives about i=100 this message appears on the screen:
> 
> gnuplot> pl '/tmp/oct-z3fdsP' u ( $ 1 ) :( $ 2 )  t "" w points 3 6  ,
> '/tmp/oct-oh3bIP' u ( $ 1 ) :( $ 2 )  t "" w points 1 4  ,
> '/tmp/oct-JbCW5P' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-qVDdwQ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-nfEEPQ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-eIgybR' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-xdN3IR' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-kKS6iS' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-PB9bRS' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-y4dZiT' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-N3kHZT' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-cAgUIU' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-VQ45pV' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-QDmI0V' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-tN8TDW' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-qPLXsX' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-NMpykY' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-ABsB5Y' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-JfYaTZ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Wj21R0' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-TNRsT1' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-8YiSS2' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-P4pKL3' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-MQa8G4' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-v9zaO5' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-q24HX6' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-NPfI07' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-CDLw68' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-7OSTIc' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-CirKng' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-N3TC0j' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-oGLXwn' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-9lKIir' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-cJAI6u' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Tk4JSy' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-ImtbyC' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-BMR6fG' u ( $FA' 1 ) :( $ 2 )  t "" w lines 2 
> 
> ^ 
>          line 0: invalid character
> 
> It's a very strange text!
> The message appears about every 100 times index. In my case, the next
> message was:
> 
> gnuplot> pl '/tmp/oct-Evyc1o' u ( $ 1 ) :( $ 2 )  t "" w points 3 6  ,
> '/tmp/oct-I2LXa4' u ( $ 1 ) :( $ 2 )  t "" w points 1 4  ,
> '/tmp/oct-A9E7rJ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-e9XaLo' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-K8WkX3' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-6ykZaJ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Wym7zo' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Czpq13' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-sZyBlJ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-oOVZHo' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-o5TWf4' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-E0s8PJ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-8oDVip' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-kGAd14' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-CmLILK' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-2qOmpq' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-E5Wv55' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-g45VWL' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-6BvjQr' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-QcSNC7' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Av34qN' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-qh4Dqt' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-qyQqs9' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-mXTBnP' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-GcE2kv' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-QuYrtb' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-YZp3DR' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Qku1Hx' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-M1ucOd' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-UKL4JR' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-cZNaIv' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-GHgqz9' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-ucVbtN' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-gYieyr' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-YRtbF5' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-wI3eFJ' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-ojMxHn' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-CNzrV1' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-gblBbG' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-GpXQkk' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-2Lm1vY' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-IWwvSC' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-mmRshh' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-OFjwzV' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-IZSa7z' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-unK0Ge' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Ar809S' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-CHpuFx' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-GkYemc' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-Me9U4Q' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-6BVcGv' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-cWdWja' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-oJlX8O' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-uBZSZt' u ( $ 1 ) :( $ 2 )  t "" w lines 2  ,
> '/tmp/oct-WcrZJ8' u ( $ 1 ) :( $ 2 )  ty�A9! "" w lines 2 
> 
> ^ 
>          line 0: invalid character
> 
>          line 0: undefined variable: set
> 
> It's bigger than the first time and in this case appears the string:
> line 0: undefined variable: set
> But the plot is right, there is no errors in the execution of the
> script. In Octave 2.1.73 with gnuplot and with octplot the messages
> not appears, only in Octave 2.9.9 compiled for my machine (no errors
> ocurred during compilation)
> 
> Can anybody help me, please?
> 
> -- 
> ***************************************** 
> José Luis García Pallero
> address@hidden
> (o<
> / / \
> V_/_
> Use Debian GNU/Linux and enjoy!
> ***************************************** 
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-- 
Geordie McBain
www.aeromech.usyd.edu.au/~mcbain