[R] complicated IF

jim holtman jholtman at gmail.com
Wed Jan 22 14:04:01 CET 2014

```Here's one way of doing it.  Does not use "complicated" IFs; just
splits the data and works on it.

> x <- read.table(text = "       Date nrec
+
+ 1 2011-07-17  667
+
+ 2 2011-07-18  266
+
+ 3 2009-10-29   29
+
+ 4 2009-10-30  211
+
+ 5 2009-10-31  237
+
+ 6 2009-11-01  898", header = TRUE, as.is = TRUE)
> # convert to Date
> x\$Date <- as.Date(x\$Date)
> # add week of year
> x\$week <- format(x\$Date, "%Y%W")
> # add the day of week
> x\$day <- format(x\$Date, "%w")
> # process each week, substituting the mean if Sunday exists
> result <- do.call(rbind
+     , lapply(split(x, x\$week), function(.week){
+         means <- mean(.week\$nrec[.week\$day %in% c('0', '5', '6')])
+         .week\$nrec[.week\$day == '0'] <- means
+         .week
+         })
+     )
>
>
> result
Date     nrec   week day
200943.3 2009-10-29  29.0000 200943   4
200943.4 2009-10-30 211.0000 200943   5
200943.5 2009-10-31 237.0000 200943   6
200943.6 2009-11-01 448.6667 200943   0
201128   2011-07-17 667.0000 201128   0
201129   2011-07-18 266.0000 201129   1
> x
Date nrec   week day
1 2011-07-17  667 201128   0
2 2011-07-18  266 201129   1
3 2009-10-29   29 200943   4
4 2009-10-30  211 200943   5
5 2009-10-31  237 200943   6
6 2009-11-01  898 200943   0
>

Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

On Wed, Jan 22, 2014 at 6:33 AM, Bill <william108 at gmail.com> wrote:
> Hello. I am trying  to work out some complicated if() logic.
> I thought of using which() and if() but cannot get it.
>
> I have a dataframe that looks like this:
>
>
>        Date nrec
>
> 1 2011-07-17  667
>
> 2 2011-07-18  266
>
> 3 2009-10-29   29
>
> 4 2009-10-30  211
>
> 5 2009-10-31  237
>
> 6 2009-11-01  898
>
> I want to take the values in nrec for consecutive Friday, Saturday and
> Sundays and average them and replace Sundays value with that average.
>
> I came up with this:
>
> deleteFridayTest[dayOfWeek(deleteFridayTest\$Date)=="Sun",]\$nrec <-
> (deleteFridayTest[dayOfWeek(deleteFridayTest\$Date)=="Sun",]\$nrec +
> deleteFridayTest[dayOfWeek(deleteFridayTest\$Date)=="Sat",]\$nrec +
> deleteFridayTest[dayOfWeek(deleteFridayTest\$Date)=="Fri",]\$nrec)/3
>
> but this won't work for my data because sometimes one or more of the days
> of data may be missing. For example Friday's data could be missing, or
> Friday and Saturday, or Sunday may be missing, or they all may be missing,
> etc.
>
> The rule I want to implement is that
> if any of Friday, Saturday, or Sunday is available then I want to have an
> entry for Sunday (call it 'X'). If all 3 days are missing then nothing
> should be done and there will be no entry for X. If any of the days Fri,
> Sat, Sun are available then X should be the "average" of those values (e.g.
> if two days are available then sum and divide by 2, if just one day is
> available then just use that value for X).
>
>  Thank you.
>
>         [[alternative HTML version deleted]]
>
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