# R Programming Language > [!NOTE]+ **External Resources** > - [W3 Schools - R Tutorial](https://www.w3schools.com/r/default.asp) ## General Tips ### Iterating Over Data Looping over dataframes should typically be avoided. ### ## R Dataframes One of the biggest differences between dataframes in R and a typical spreadsheet is that rows can have their own name associated with them - [ ] Mapping two different frames together - [ ] Finding Duplicates ### Subsetting Dataframes **Dataframe Indexing:** `df[,]` - The comma separates the row indices from the column indices. - An empty space in either position indicates all rows/columns respectively. - Ex: `df[df$id > 1,]` → “Rows in `df` whose `id` value is greater than 1.” - Ex: `df[1:10,]` → “The first 10 rows in `df`.” ---