r - Merge for multiple columns and rows -

given following data tables:

> d1 <- data.table(letter=c("a", "b", "a", "b"), v1=c(0,0,0,0),v2=c(0,0,0,0)) > d2 <- data.table(letter=c("a", "b"), value=c(1,2)) > d1    letter v1 v2 1:       0  0 2:      b  0  0 3:       0  0 4:      b  0  0 > d2    letter value 1:          1 2:      b     2 

i seek fill columns v1 , v2 d1 using values d2, that:

> d12    letter v1 v2 1:       1  1 2:      b  2  2 3:       1  1 4:      b  2  2 

i assume have use function 'merge' somehow have not managed.

any advice on how achieve this?

many in advance!

setkey(d1, letter) setkey(d2, letter) d1[d2, c('v1','v2'):=value] # d1 holds updated dt 

the d1[d2] merges d1 d2; c('v1', 'v2'):=value assigns value column v1 , v2. rows in d1 have letters not in d2 left as-is.