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Selecting 3 different hours in a day

3 messages · jck13, Jeff Newmiller, jim holtman

#
Hello,

I have a csv with 5months of hourly data for 4 years. I would like to get
9am, 12pm and 3pm from each day  and create a subset or a new data frame
that I can analyze. The time are from hour 0-23 for each day.
I am not sure how to create a loop which will take out each of these hours
and create a subset.

I was thinking of doing a for loop using the row number since:
9am= row 10
12pm= row 13
3pm= row 16

trying to loop through to extract these 3 times each day.

n=length(date_stamp)
             
for (i in i:n) {
m= 10
i= 1
new1= mv[m,]
i= i+1
m= m+3
##m+18 at row 16?
}

I need some help creating a loop through this! Thank you! 


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#
No data sample was provided, so with a verbal description of the problem comes a verbal answer.

I would use expand.grid to build a set of all desired date/time combinations, then use the merge function to select rows in your actual data.
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jck13 <jennakeane at hotmail.com> wrote:

            
#
attach another column to you dataframe with the hour of the day and then use 'subset' to collect the three hours of interest.

Sent from my iPad
On Nov 8, 2011, at 1:12, jck13 <jennakeane at hotmail.com> wrote: