CODEWITHSUNDEEP
rdate
chilland
chilland

Reputation: 69

Count/frequency of observations by month

I have a dataset with 34 variables and about 25,000 observations. Each observation refers to a specific incident. Its formatted something like this:

  no    id    date         ....
1 363   006   2005-11-05
2 939   012   2007-01-23
3 541   090   2009-06-14

I'm wondering if someone could walk me through how to get the total number of incidents for each month over the 5 years contained in this dataset.

Upvotes: 3

Views: 7006

Answers (2)

David
David

Reputation: 9405

It seems like you just want to count the number of rows for each month, if so you can just use table():

> #make junk data
> data <- data.frame(no=rnorm(100),id=rnorm(100),date=seq(Sys.Date()-99,Sys.Date(),by="day"))
> table(format(data$date,"%b-%Y"))
Aug-2013 Jul-2013 Nov-2013 Oct-2013 Sep-2013 
      31        7        1       31       30

Upvotes: 5

IRTFM
IRTFM

Reputation: 263301

tapply( dfrm$no, sub(".+-(.+)-.+", "\\1", dfrm$date), sum, na.rm=TRUE)

For month and year in MM-YYYY format use this as you category code:

.... , sub("(.+)-(.+)-.+", "\\2-\\1", data$date) , ....

Upvotes: 0

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