Rstudio Server eating up memory

We recently installed RStudio Server on a CentOS box. It has 15GB right now of RAM. I have a script that I run on my Macbook Pro that I placed on the server and when it runs on the server, it's eating up just over half the available memory. When I run it on my Mac using RStudio Desktop it uses hardly any RAM. Any ideas? It doesn't do anything crazy and the datasets don't breach 1M rows, so nothing is very large.