I'm new to programming in R, and programming in general. I have a dataframe 'd' with columns Rating, Type, Source, Prob and some 200 rows. Can anyone tell me how I would best go about creating a new dataframe 'd_A' from an existing dataframe 'd' selecting (creating new dataframe from) only rows from 'd' where the value in the first column 'Rating' (d$Rating) is EITHER 'A-' or 'A+'?
This is smaller version of 'd': enter image description here
Many thanks in advance :)