r - ddply multiple quantiles by group

Question

how can I do this calculation:

library(ddply)
quantile(baseball$ab)
  0%  25%  50%  75% 100% 
  0   25  131  435  705 

by groups, say by "team"? I want a data.frame with rownames "team" and column names "0% 25% 50% 75% 100%", i.e. one quantile call per group.

doing

ddply(baseball,"team",quantile(ab))

is not the correct solution. my problem is that the OUTPUT of each grouped operation is a vector of length 5 here.

in other words, what's a neat solution to this (nevermind the header):

m=data.frame()
for (i in unique(baseball$team)){m=rbind(m,quantile(baseball[baseball$team==i, ]$ab))}
head(m,3)
  X120 X120.1 X120.2 X120.3 X120.4
1  120  120.0  120.0 120.00    120
2  162  162.0  162.0 162.00    162
3   89   89.0   89.0  89.00     89

Answer 1

With base R you could use tapply and do.call

library(plyr)
do.call("rbind", tapply(baseball$ab, baseball$team, quantile))

do.call("rbind", tapply(baseball$ab, baseball$team, quantile, c(0.05, 0.1, 0.2)))

Or, with ddply

ddply(baseball, .(team), function(x) quantile(x$ab))