Aggregate a data frame in R by equally spaced time intervals

Question

I want to aggregate the data by time and create equally spaced time intervals:

date<- c(as.POSIXct("2011-08-08 21:00:00"), as.POSIXct("2011-08-08 21:26:00"))
value<-c(1,2)
dt<-data.frame(date, value)

DT<-aggregate(cbind(dt$value),list(cut(dt$date, breaks="10 min")),sum) 

dt:
2011-08-08 21:00:00 1
2011-08-08 21:26:00 2

DT:
2011-08-08 21:00:00 1
2011-08-08 21:20:00 2

What I want:

2011-08-08 21:00:00 1
2011-08-08 21:10:00 NA
2011-08-08 21:20:00 2

Is there anyway to do this without using zoo or xts?

Answer 1

I'm assuming by your last line that you are trying to avoid using packages.

Sticking with base R, you can try tapply, but your dates will become the rownames (or names, if you skip the data.frame step):

data.frame(value = tapply(cbind(dt$value),
                          list(cut(dt$date, breaks="10 min")),
                          sum))
#                     value
# 2011-08-08 21:00:00     1
# 2011-08-08 21:10:00    NA
# 2011-08-08 21:20:00     2