plotting a discrete function

[PyMarc2]

I tried plotting

self.getEquation = self.dutyCycle * Sum(((2/(n*pi))*sin(pi*n*self.dutyCycle) * cos(2*pi*n*t/self.period)), (n, 1, 2))
signalPlot = plot(self.getEquation)
signalPlot.show()

UserWarning: The evaluation of the expression is problematic. We are trying a failback method that may still work. Please report this as a bug.

[oscarbenjamin]

Can you show the code to reproduce this (including defining symbols). Otherwise could you show the repr and srepr of self.getEquation?

[oscargus]

I can confirm the problem (replaced the unknowns with 0.1 just for the sake of it). However, applying .doit() allows it to plot, which can be some sort of hint both to get around the problem and maybe even to solve it (probably the unevaluated Sum causing it).

[ishanaj]

Issue #16572 might be related.