sahil desai sahil desai - 3 months ago 9
R Question

Replace the value in column with respect to other two columns values


Data1
A B C
a 1 a,b
b 6 c,b
c 5 b,c
d 3 a,d



So now i want to make new column "D"

where it replace values as per column A and B values, for example.


C D
a,b 1,6
c,b 5,6
b,c 6,5
a,d 1,3


Answer

We can use chartr. Create the old and new arguments for chartr by pasteing the key/value columns i.e. 'A' and 'B' and use x as the 'C' column to replace the substring in 'C' that matches with 'A' to that of 'B'

Data1$D <- with(Data1, chartr(paste(A,collapse=""), paste(B,collapse=""), C))
Data1$D
#[1] "1,6" "5,6" "6,5" "1,3"

Update

This should also work if the 'x' is from a different dataset

with(Data1, chartr(paste(A,collapse=""), paste(B,collapse=""), Data2$Col1))
#[1] "1,5" "6,3" "1,1" "1,5"

data

Data1 <- structure(list(A = c("a", "b", "c", "d"), B = c(1L, 6L, 5L, 3L
), C = c("a,b", "c,b", "b,c", "a,d")), .Names = c("A", "B", "C"
), class = "data.frame", row.names = c(NA, -4L))

Data2 <- data.frame(Col1 = c("a,c", "b,d", "a,a", "a,c"), stringsAsFactors=FALSE)