Best resources for learning R, with Python (pandas, sklearn, scipy, numpy) background?

At my job I need to pick up R to manipulate some datasets. I've been using pandas quite a bit and need to duplicate what I've been doing in pandas in R. I most frequently use simple functions like merging dataframes, computing correlations, selecting certain columns of dataframes. I also use mixed models.

Thanks!

datascience learning numpy pandas python resources scipy sklearn