I've found some source code that creates a visualization I like. I've (slightly) modified it and used exclusively my own data in it. Is it right to cite the github repository I acquired the original code from? I don't want to be improper or misleading at all, but then it's not normal to cite matplotlib, say, which this doesn't feel much different to (except it's code from a single author) so I'm unsure on correct procedure. I'm trying not to inflate the word count unnecessarily or give the false impression that the data is someone else's (which I'm worried citing the code might do) - but equally I don't want to give off any false impressions of authorship on my part.
Edit: To clarify I'm not distributing the code at all, I'm just using it to generate a figure in my paper.