[R] Count observation based on hour

arun
Thu, 06 Feb 2014 22:34:03 -0000

HI Map,
I am not sure what you really wanted.? Perhaps, this helps:

dat <- structure(list(Date = c("2014-01-01 00:00:00",
"2014-01-02 11:00:00",
"2014-01-02 22:00:00", "2014-01-03 03:00:00",
"2014-01-01 00:00:00",
"2014-02-02 11:00:00", "2014-02-02 22:00:00",
"2014-02-03 03:00:00",
"2014-02-01 00:00:00", "2014-03-01 11:00:00",
"2014-03-02 22:00:00",
"2014-03-03 03:00:00", "2014-03-01 00:00:00",
"2014-03-01 11:00:00",
"2014-03-02 22:00:00", "2014-01-03 03:00:00")), .Names =
"Date", class = "data.frame", row.names = c("1",
"2", "3", "4", "5", "6",
"7", "8", "9", "10", "11",
"12", "13",
"14", "15", "16"))
dat$Date <- as.POSIXct(dat$Date)
res <- as.data.frame(table(
with(dat,cut(Date,breaks=seq(min(Date),max(Date)+3600,by= '1 hour')))))
A.K.



Hi AK,

Thanks for the tips! But it doesn't seem to work for some
reasons. ?Basically I want to do a time series analysis and I heard that
 it is actually very easy to perform hourly count, e.g. count the number
 of occurrence hourly when the variable is in date-time format like
this: YYYY-MM-DD HH:MM:SS. ?

I was thinking a 'long' way (sorry for this if it sounds stupid
:p) by dividing my data into say 1000 24-hr (i.e. one day) sections,
count them all them merge... Anyway, could you give me more advice on
this please? ?Thanks!

Map



On Wednesday, February 5, 2014 10:59 AM, arun <smartpink111 at yahoo.com>
wrote:
Hi,
Try:

data.frame(table(dat$Date))
A.K.


Hi guys, I have some 20,000 observations like this:
? ? ? ? ? Date ? ? ?
2014-01-01 00:00:00
2014-01-02 11:00:00
2014-01-02 22:00:00
2014-01-03 03:00:00

I want to perform an hourly count (e.g. the frequency occur at
each hour for a specific date) so the result would look like this:

? ? ? ? ? Date ? ? ? ? ? ? ? ? ? ?Frequency
2014-01-01 00:00:00 ? ? ? ? ? ? 1
2014-01-01 01:00:00 ? ? ? ? ? ? 1
2014-01-01 02:00:00 ? ? ? ? ? ? 1
2014-01-01 03:00:00 ? ? ? ? ? ? 1

Any suggestions? ?Thanks!