Earliest Date for each id in R

Question

I have a dataset where each individual (id) has an e_date, and since each individual could have more than one e_date, I\'m trying to get the earli

Answer 1

You may use library(sqldf) to get the minimum date as follows:

data1<-data.frame(id=c("789","123","456","123","123","456","789"),
                  e_date=c("2016-05-01","2016-07-02","2016-08-25","2015-12-11","2014-03-01","2015-07-08","2015-12-11"))  

library(sqldf)
data2 = sqldf("SELECT id,
                    min(e_date) as 'earliest_date'
                    FROM data1 GROUP BY 1", method = "name__class")    

head(data2)   

id earliest_date
123 2014-03-01
456 2015-07-08
789 2015-12-11