CDF with a massive amount of data
My estimate is that there are around 5.4b numbers in your dataset, all in the range of 0-50 according to your comment. I doubt there are much faster ways to do this on all the data than you are currently doing. However if you would just take every file and get random samples of 0.1-10% of each file and then combine these, you will still get an ecdf that is visually almost exactly the same while reducing memory issues and computing power necessary.