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.
You just need to add a line
plt.show()
Then it will work. You can also save the file before showing
plt.savefig("*imageName*.png")
Matplotlib with Pydroid 3 on Android: how to see graph?