Convert data frame common rows to columns

Question

Say I have a data frame where one column is some repeating value (dates, IDs, etc). Is there a way to convert a data frame into a now data frame with columns instead of rep

Answer 1

If there are always equal numbers of observations in each group, this would be very easy with split then as.data.frame

as.data.frame(split(d$c, d$b))
#    aa bb cc
# 1  30 50 50
# 2  45 35 40
# 3  30 40 40
# 4  50 40 50
# 5  50 20 40
# 6  20 50 40
# 7  35 25 35
# 8  50 20 40
# 9  35 30 30
# 10 35 50 25