R calculate the average of one column corresponding to each bin of another column [duplicate]

Answer 1

As @Fernando already mentioned in his comment you could try cut (binning) and tapply:

tapply(df$f, cut(df$r, seq(15, 70, by=5)), mean)
# (15,20]  (20,25]  (25,30]  (30,35]  (35,40]  (40,45]  (45,50]  (50,55]  (55,60]  (60,65]  (65,70] 
#17.68433 18.55918 19.28683 20.49000 20.87942 20.65430 20.96155 21.35146 21.92259 22.57414 21.74700 

Answer 2

Alternatively, you can use the wonderful plyr package.

library(plyr)
ddply(df, .(cut(df$r, 5)), colwise(mean))

However, if you have to ask a question like the above, you are just fine with the tapply solution.