Thanks for your response. I am not looking to save the image. It is already saved and I am looking to use {Width=10%, Height=10%} to resize it. The issue is {Width=10%, Height=10%} doesn't seem to work although it is referenced online.
I had seen in the OP that the image was not being generated in the script, but imported. Hence my suggestion.
Too much of data science degenerates into fiddling with reports so that they look good, which can be time better spent with the data and its analysis. My own preference is to defer presentation as long as possible and then deal with all the picky stuff in one pass.
There are alternate approaches to dealing with the image size problem:
At the source, as I suggested
Post-processing with the {egg} package, possibly
Post processing externally by saving to pdf and re-sizing in a vector editor