Citing author of visualization source code? 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.
If the software achieves something that would not be readily obvious to most practitioners in your field then it's appropriate to cite it.

A software package for doing line graphs or box-and-whisker plots does not need to be cited, as both visualizations are widely used and understood. I.e. we don't want to know or care that you used MATLAB vs Excel to plot data.

If the visualization is novel or non-obvious then it would be appropriate to cite the person who created the visualization technique. If the software you use does a non-trivial amount of work to create the visualization then it would be appropriate to cite the tool you used to create it. 

For example, I would judge the amount of work done to create a box-and-whisker plot (computing the quartiles of a data set) to be obvious and not worth citation. The technique itself is ubiquitous at this point, and nobody cares what software you used to generate it. On the other hand, a software package that automatically picks out and highlights human organs within an MRI scan data set is a unique tool that probably deserves citation.

If you're still not sure, ask your adviser, as they will best know what will be obvious vs. interesting to your community.

Lastly, read the software README or license to see if they have a suggested citation format. Oftentimes academic software products will ask that you cite the paper which explains the software rather than their website, since the paper citations are more valuable than website citations.