[Maxima] plotting problem with trigonometric functions
toy.raymond at gmail.com
Thu Mar 15 11:02:18 CDT 2012
On Wed, Mar 14, 2012 at 12:46 PM, Jaime Villate <villate at fe.up.pt> wrote:
> On 03/14/2012 04:50 PM, Raymond Toy wrote:
>> Hmm. I see a similar thing, but it's not maxima. Maxima returns almost
>> instantly, but gnuplot is sucking up 100% cpu plotting a (mostly) constant.
>> Not sure why that is because plot2d(1,[x,-1,1]) brings up a plot instantly.
>> So it's not a maxima problem per se.
> plot2d(sec(x)*cos(x),[x,-1,1],**[plot_format,xmaxima]) works fine.
> But even being a Gnuplot issue, this suggests that we could use something
> such as fpprintprec: 14
> when creating the data file for Gnuplot. In any case no graphic display
> will be able to use more than 14 digits for a plot (I think!).
That's true, but consider this particular example. sec(x)*cos(x) isn't
always exactly 1 because of numerical issues in computing sec and cos.
Sometimes it's nice to be able to see that in a plot. If you make maxima
only print 14 digits, this difference goes a way. (Yes, it might be better
to plot sec(x)*cos(x)-1, but that adds yet another round-off.)
> Is anyone against that I go ahead and do such change in plot2d?
So, I guess I'm (slightly) opposed to this change. It's definitely not a
maxima problem, and we should let the gnuplot folks know about it. Or
recommend a version of gnuplot that doesn't seem to have this problem (if
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Maxima