For Loops
R For Loops
Loops are a useful part of many programming languages but are perhaps used in more limited ways in R due to the extensive use of “Vectorization”.
“Most of R’s functions are vectorized, meaning that the function will operate on all elements of a vector without needing to loop through and act on each element one at a time. This makes writing code more concise, easy to read, and less error prone.”
Vectorization approaches are also used extensively within dataframes.
The general structure of a for loop is:
The sequence is a vector/list and val takes on each of element of the sequence in turn during the loop. In each iteration, the main code is evaluated in conjunction with that value.
Task 1
Copy the provided test code and run it
Task 2
Try a vectorised alternative
You can investigate the commands/functions cat and paste further using R help e.g: ?cat
But some tasks do lend themselves to for loops, in particular reading things from or writing things to files
Task 3
Copy the provided test code, that saves some dataframes as files, and run it
Task 4
Check the resulting files in the RStudio ‘Files’ tab
Can you see the difference between paste and paste0?