[R] Extracting dates to create a new variable

[Farnoosh Sheikhi]

Hi there, 
I have a data set like below and wanted to create a new date variable by extracting the dates for specific departments.I want to extract the dates for departments CC, DD, FF,  put it in a new column and repeat it for other unique IDs.
Subject<- c("2", "2", "2", "3", "3", "3", "4", "4", "5", "5", "5", "5")dates<-seq(as.Date('2011-01-01'),as.Date('2011-01-12'),by = 1) deps<-c("A", "B", "CC", "C", "CC", "A", "F", "DD", "A", "F", "FF", "D")df <- data.frame(Subject, dates, deps)df
The final data set should look like this:newdate<-c(" 2011-01-03",  "2011-01-03",  "2011-01-03", "2011-01-05", "2011-01-05", "2011-01-05" , "2011-01-08", "2011-01-08", "2011-01-08", "2011-01-11", "2011-01-11", "2011-01-11")final<-data.frame(Subject, dates, deps, newdate)final
I really appreciate any help.
 Best,Farnoosh


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