[Maxima] Plotting bug?

Andrej Vodopivec andrej.vodopivec at gmail.com
Fri Nov 30 10:16:26 CST 2007


On Nov 30, 2007 4:02 AM, Rob Frohne <frohro at wallawalla.edu> wrote:
> Hi Everyone,
>
> I find a funny thing happening when I plot with this command:
>
> plot2d([realpart(ev(sum(%e^(-2*%i*%pi*f*k),k,-50,50),simpsum))], [f,-2,2],[y,-50,50]);
>
> The problem is that certain ranges give constant and incorrect values on
> the plot.  I can send a screenshot to anyone interested.  If I change
> the f plot range, the blanks disappear and it works.  It also works
> sometimes for different numbers of terms in the sum.   Where
> should I report this bug?  If I am the best person to try and figure it
> out, is there a debugger or something I can use to trace what is
> happening in the plot command?


When the plot does not look correct because of some properties of the
function, the best solution is to increase the number of points in
which the function value is computed. The following will produce a
better plot:

plot2d([realpart(ev(sum(%e^(-2*%i*%pi*f*k),k,-50,50),simpsum))],
[f,-2,2],[y,-50,50], [nticks, 20]);

I don't think it is a bug that the default values do not produce nice
plots for all inputs.

-- 
Andrej


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