paste, by and data.table in r

Question

I\'m trying to paste strings from a reshaped dataset. I\'m using the data.table package as follows:

m<-data.frame(x=rep(c(\"a\",\"b\"),20),y=factor(sample         


        

Answer 1

For completeness' sake, an official answer:

If you use paste(y,collapse=",") instead, it should work.

Answer 2

The toString(y) function produced the same result as paste(y, collapse = ", "), I use it as substitute for the longer paste version. So

DT[, toString(y), by = x]

would yield the outcome

#   x                                                         V1
#1: a v, o, q, p, t, c, y, d, n, r, o, k, v, r, t, n, e, f, g, u
#2: b y, j, t, l, w, r, s, w, b, x, h, j, o, k, a, c, r, c, b, e

which is the same for paste

DT[, paste(y, collapse = ", "), by = x]