How to concatenate strings in a specified order

问题

Tried to concatenate strings diagonally from this post how to alternatively concatenate 3 strings, but was not successful.

My input is:

a<-c("a1","a2","a3")
b<-c("b1","b2","b3")
c<-c("c1","c2","c3")

My expected output would be

   "a1" "b2" "c3" "a2" "b3" "a3"

How to get the above from

  c(rbind(a,b,c))  

回答1:

How about ordering the vector by values derived by the row and columns after setting the lower diagonal to missing

mat <- rbind(a,b,c)

mat[lower.tri(mat)] <- NA
na.omit(mat[order(col(mat) - row(mat))])

回答2:

One way would be to tweak Mark's solution

as.vector(na.omit(c(sapply(1:3, function(i) c(a[i], b[i+1], c[i+2])))))
#[1] "a1" "b2" "c3" "a2" "b3" "a3"

Also,

 vec1 <- c(a,b,c)
 indx <- seq(1,length(vec1), by=4)+rep(0:2,each=3)
 indx1 <- indx[indx <= length(vec1)]
 vec1[indx1[-length(indx1)]]
 #[1] "a1" "b2" "c3" "a2" "b3" "a3"

来源：https://stackoverflow.com/questions/24351451/how-to-concatenate-strings-in-a-specified-order