Why R?

I started working on R recently. The thing I like most about R is it is open source. R has many contributed packages for various domains. I am still exploring the capability and limitations of R in Machine learning and data mining domain. R comes with lots of statistical and machine learning tools. I ran k-means clustering algorithm on a sample dataset, the script was short and easier to code. I have to see how the k-means algorithm in R will scale for larger dataset.