Subsetting dataframe by all factor levels
I need to learn geospatial analyses in R to complement my GIS knowledge. I've just re-read the subsetting chapter in Hadley's 'Advanced R' without seeing how to create separate data frames based by extracting all rows for each site name in the parent data frame in one step. I believe that what I need to do is create a list of the factor names and feed them to a loop subsetting each to a new dataframe. Perhaps there's a better way unknown to me and I need advice, suggestions, and recommendations how to proceed. The inclusive data frame has this structure: str(rainfall) 'data.frame': 113569 obs. of 6 variables: $ name : Factor w/ 58 levels "Blazed Alder",..: 20 20 20 20 20 20 20 ... $ easting : num 2370575 2370575 2370575 2370575 2370575 ... $ northing: num 199338 199338 199338 199338 199338 ... $ elev : num 228 228 228 228 228 228 228 228 228 228 ... $ sampdate: Date, format: "2005-01-01" "2005-01-02" ... $ prcp : num 0.59 0.08 0.1 0 0 0.02 0.05 0.1 0 0.02 ... My goal is to use the monthly mean rainfall at each of the 58 reporting stations to interpolate/extrapolate rainfall over the entire county for selected years to show variability. The data points are not evenly distributed but clustered in more populated areas and dispersed in rural areas. My geochemical data typically are like this and I need to also learn how this distribution affects how the data are analyzed. TIA, Rich