Assign a matrix to a subset of a data.table
问题 I would like to assign a matrix to a multi-column subset of a data.table but the matrix ends up getting treated as a column vector. For example, dt1 <- data.table(a1=rnorm(5), a2=rnorm(5), a3=rnorm(5)) m1 <- matrix(rnorm(10), ncol=2) dt1[,c("a1","a2")] <- m1 Warning messages: 1: In `[<-.data.table`(`*tmp*`, , c("a1", "a2"), value = c(-0.308851784175091, : 2 column matrix RHS of := will be treated as one vector 2: In `[<-.data.table`(`*tmp*`, , c("a1", "a2"), value = c(-0.308851784175091, :