aggregate()
- это то, что вы ищете.Попробуйте это:
aggregate(desc ~ sol, data = df, paste, collapse = ",")
sol desc
1 1 fry, toast,frt,grt,gty,ytr,uyt,ytr
2 4 hyg,hyu,loi,opu,yut,yut
3 6 hyt, ytr,oiu
Данные
df <- structure(list(sol = c(1L, 1L, 1L, 6L, 4L, 4L), desc = c("fry, toast",
"frt,grt,gty", "ytr,uyt,ytr", "hyt, ytr,oiu", "hyg,hyu,loi",
"opu,yut,yut")), .Names = c("sol", "desc"), class = "data.frame", row.names = c(NA,
-6L))