CODEWITHSUNDEEP
rmergematching
user2327621
user2327621

Reputation: 997

Merging two data frames in R by matching key

I have two data frames DFS and DFE. DFS has the start dates at which a set of employees started a job. and DFE has the end dates at which they completed the job. The order in which the employee IDs appear in the two frames may be different. 

DFS <- data.frame(ID=c('ID1','ID2','ID3'), begin=c('3/1/06 18:20', '2/1/07 15:30', '5/3/06 9:00'));
DFE <- data.frame(ID=c('ID3', 'ID2','ID1'), end=c('4/1/10 12:00', '6/1/11 14:20', '1/1/09 11:10'));

I want to create a data frame that matches the begin end end dates for each employee (e.g. output below):

DFR <-data.frame(ID=c('ID1','ID2','ID3'), begin=c('3/1/06 18:20', '2/1/07 15:30', '5/3/06 9:00'),
               end=c('1/1/09 11:10', '6/1/11 14:20','4/1/10 12:00' )  );

This can be done in a loop. But I would like to know if there is an alternative method for matching and merging in R that does not involve loops. Thanks for your help.

Upvotes: 3

Views: 9268

Answers (1)

Matthew Lundberg
Matthew Lundberg

Reputation: 42689

merge does what you want. It will create a data frame of the joined data. Here, you want to join on the ID column, which is specified with by.

by defaults to the intersection of the column names between the data frames, so if there are no other common columns, it need not be specified.

merge(DFS, DFE, by='ID')
##    ID        begin          end
## 1 ID1 3/1/06 18:20 1/1/09 11:10
## 2 ID2 2/1/07 15:30 6/1/11 14:20
## 3 ID3  5/3/06 9:00 4/1/10 12:00

Upvotes: 7

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