r - long to wide format, but without condition

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65836078/long-to-wide-format-but-without-condition

Answer 1

Here is an option with aggregate from base R

aggregate(City ~ ID, df1, toString)

-output

# ID                  City
#1  x         Paris, Madrid
#2  y Paris, Prague, Moscow
#3  z                Moscow

data

df1 <- structure(list(ID = c("x", "x", "y", "y", "y", "z"), City = c("Paris", 
"Madrid", "Paris", "Prague", "Moscow", "Moscow")), class = "data.frame",
row.names = c(NA, 
-6L))