If you want to create rainfall maps for the whole world in R there is no readily available code or package to do this. Moreover, data publicly available from research institutions is not generally in plain text format or other familiar formats. Hydrological and climatological studies sometimes require rainfall data over the entire world for long periods of time. The Climate Prediction Center’s (CPC) site, daily data from 1979 to present, is a good resource. This data is available at CPC’s ftp site (ftp://ftp.cpc.ncep.noaa.gov/precip/CPC_UNI_PRCP/GAUGE_GLB/).
I created R code to download rain/snow (or precipitation to be scientific) data from the CPC’s ftp site and plot it. All my code is available at my GitHub site – https://github.com/RationShop/cpcRain.
The Rmarkdown document showing some examples is at my RPubs site – http://rpubs.com/RationShop/cpcRain