[R] Selecting 3 different hours in a day

[Jeff Newmiller]

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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Sent from my phone. Please excuse my brevity.

jck13 <jennakeane at hotmail.com> wrote:

>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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>
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