I'm currently using an Android device (of Samsung), Pydroid 3.
I tried to see any graphs, but it doesn't works.
When I run the code, it just shows me a black-blank screen temporarily and then goes back to the source code editing window.
(means that i can't see even terminal screen, which always showed me [Program Finished])  
Well, even the basic sample code which Pydroid gives me doesn't show me the  graph :(
I've seen many tutorials which successfully showed graphs, but well, mine can't do that things.
Unfortunately, cannot grab any errors.
Using same code which worked at Windows, so don't think the code has problem.
Of course, matplotlib is installed, numpy is also installed.
If there's any possible problems, please let me know.
I also had this problem a while back, and managed to fix it by using plt.show()
at the end of your code. With matplotlib.pyplot as plt.
Matplotlib with Pydroid 3 on Android: how to see graph?