Point shape in ggplot2 with distance matrix

Sorry but your code is not actually reproducible since we don't have access to "matrixbc.txt" file, and it's not pretty clear what you want to achieve, could you elaborate a little more in your question? Also, please narrow down your code to just the relevant section (only include the libraries relevant to your issue).

Maybe this FAQ would give you a better idea of how to make a proper reprex