CODEWITHSUNDEEP
rmergedataframe
Jota
Jota

Reputation: 17621

Merging data frames in R

Let's say I have two data frames. Each has a DAY, a MONTH, and a YEAR column along with one other variable, C and P, respectively. I want to merge the two data frames in two different ways. First, I merge by data:

test<-merge(data1,data2,by.x=c("DAY","MONTH","YEAR"),by.y=c("DAY","MONTH","YEAR"),all.x=T,all.y=F)

This works perfectly. The second merge is the one I'm having trouble with. So, I currently I have merged the value for January 5, 1996 from data1 and the value for January 5, 1996 from data2 into one data frame, but now I would like to merge a third value onto each row of the new data frame. Specifically, I want to merge the value for Jan 4, 1996 from data2 with the two values from January 5, 1996. Any tips on getting merge to be flexible in this way?

sample data:

data1
C DAY MONTH YEAR
1   1     1 1996
6   5     1 1996
5   8     1 1996
3  11     1 1996
9  13     1 1996
2  14     1 1996
3  15     1 1996
4  17     1 1996    

data2
P DAY MONTH YEAR
1   1     1 1996
4   2     1 1996
8   3     1 1996
2   4     1 1996
5   5     1 1996
2   6     1 1996
7   7     1 1996
4   8     1 1996
6   9     1 1996
1  10     1 1996
7  11     1 1996
3  12     1 1996
2  13     1 1996
2  14     1 1996
5  15     1 1996
9  16     1 1996
1  17     1 1996

Upvotes: 1

Views: 1142

Answers (1)

frankc
frankc

Reputation: 11483

Make a new column that is a Date type, not just some day,month,year integers. You can use as.Date() to do this, though you will need to look up the right format the format= argument given your string. Let's call that column D1. Now do data1$D2 = data1$D1 + 1. The key point here is that Date types allow simple date arithmetic. Now just merge by x=D1 and y=D2.

In case that was confusing, the bottom line is that you need to covert you columns to Date types so that you can do date arithmetic.

Upvotes: 2

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