CODEWITHSUNDEEP
r
hjw
hjw

Reputation: 1289

Comparing 2 data frames and writing the result to a 3rd

I have 2 data frames with identical dimensions A,B. First column of each data frame is a date. I would like to create a 3rd data frame that has 0s where A < B and 1s where A > B where the comparison is done element wise excluding the date column. This is what I have done so far which works without looping.

C = A
C[] = 0
temp = unlist(as.relistable(as.matrix(C[-1])))
temp[which(A[-1]>B[-1])] = 1
C = data.frame(C[1], relist(temp))

But it seems like there has to be an easier way to do this (especially given the data.frame dimensions are identical).

Generically, what is the proper method of comparing 2 data frames element wise and writing the result to a 3rd data frame?

Upvotes: 0

Views: 90

Answers (1)

Simon O&#39;Hanlon
Simon O&#39;Hanlon

Reputation: 59970

TRUE and FALSE are 1 and 0 repsectively so you should just be able to do this...

C <- ( A > B ) + 0

To exclude the first column just use [ to subset it like this:

C <- ( A[,-1] > B[,-1] ) + 0

And by way of example:

A <- data.frame( Date1 = as.POSIXct( Sys.Date()+101:105 ) , Date2 = as.POSIXct( Sys.Date()-1001:1005 ) )
#       Date1      Date2
#1 2013-12-13 2010-12-07
#2 2013-12-14 2010-12-06
#3 2013-12-15 2010-12-05
#4 2013-12-16 2010-12-04
#5 2013-12-17 2010-12-03

B <- data.frame( Date1 = as.POSIXct( Sys.Date()+106:110 ) , Date2 = as.POSIXct( Sys.Date()-1006:1010 ) )
#       Date1      Date2
#1 2013-12-18 2010-12-02
#2 2013-12-19 2010-12-01
#3 2013-12-20 2010-11-30
#4 2013-12-21 2010-11-29
#5 2013-12-22 2010-11-28

C <- ( A > B ) + 0

#     Date1 Date2
#[1,]     0     1
#[2,]     0     1
#[3,]     0     1
#[4,]     0     1
#[5,]     0     1

Upvotes: 2

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