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woodman
2024 Nov 27
4
R Processing dataframe by group - equivalent to SAS by group processing with a first. and retain statments
Check out the dplyr package, specifically the mutate function.
# Create new column based on existing column value
df <- df %>% mutate(FirstDay = if(ID = 2, 5))
df
Repeat as needed to capture all of the day/firstday combinations you want to account for.
Like everything else in R, there are probably at least a dozen other ways to do this, between base R and all of the library packages