Why is there no apply.hourly in R with xts/zoo?

Question

I want to aggregate data by hourly mean. Daily is very easy:

apply.daily(X2,mean)

Why is there no function for hourly? I tried

hr.means <- aggregate(X2, format(X2["timestamp"],"%Y-%m-%d %H"))

and got always error with trim argument. Is there an easier function similar to apply.daily? What if I want to aggregate the mean of 5 minutes. Data are values per minute:

"timestamp", value 
"2012-04-09 05:03:00",2
"2012-04-09 05:04:00",4
"2012-04-09 05:05:00",5
"2012-04-09 05:06:00",0
"2012-04-09 05:07:00",0
"2012-04-09 05:08:00",3
"2012-04-09 05:09:00",0
"2012-04-09 05:10:00",1

I am using xts and zoo.

Answer 1

try

period.apply(X2, endpoints(X2, "hours"), mean)

apply.daily is simply a wrapper for the above:

> apply.daily
function (x, FUN, ...)
{
    ep <- endpoints(x, "days")
    period.apply(x, ep, FUN, ...)
}

Answer 2

hr.means <- aggregate(X2, format(time(X2),"%y-%m-%d %H"), mean) 

This should work fine.