Re: [R] R loop

From: Moshe Olshansky <m_olshansky_at_yahoo.com>
Date: Thu, 05 Jun 2008 22:03:15 -0700 (PDT)


Hi Andy,

I see two problems:

First of all, it must be a$wk[i] <- 1 and not a$wk <- 1, since this way it makes all 10 entries of a$wk to be 1. But R won't complain about this!

What R should complain about is your loop. If you write for (i in a$date) it means that i loops between all the VALUES in a$date, not their indexes (i.e. i will be "2008-01-01" 4 times, "2008-01-14" 4 times, etc). So replace your loop by for (i in 1:length(a$date)) or alternatively your condition should be if (i > set) and not if (a$date[i] > set) since a$date[as.Date("2008-01-01")] doesn't make much sense. But if you do this you will have problem changing the appropriate value of a$wk.

> From: Andrew McFadden <Andrew.McFadden_at_maf.govt.nz>
> Subject: [R] R loop
> To: r-help@r-project.org
> Received: Friday, 6 June, 2008, 1:46 PM
> I all
>
> I am just trying to get the idea of a loop if statement for
> another
> purpose. I was going to label a new variable based on date
> ie first week
> 1, second week 2 etc. My code in bold is wrong but seems
> logical to me,
> could someone help.
>
> x <-
> rep(c(2660156,2663703,2658165,2659303,2661531,2660914),c(2,2,2,2,1,1))
> y <-
> rep(c(6476767,6475013,6475487,6479659,6477004,6476388),c(2,2,2,2,1,1))
> date <-
> rep(as.Date(c("2008-01-01","2008-01-14","2008-01-28"),
> format
> = "%Y-%m-%d"),c(4,4,2))
> a<-data.frame(x,y,date)
> a$wk<-rep(c(0),nrow(a))
> a
> set<-as.Date(c("2008-01-01"), format =
> "%Y-%m-%d")
> set
>
> for(i in a$date){
> if (a$date[i]>set & a$date[i]<set +7
> ){a$wk<-1}else
> if (a$date[i]>set +7){a$wk<-2}else {a$wk<-3}
> }
> a
>
> Kind regards
>
> andy
>
> Andrew McFadden MVS BVSc
> Incursion Investigator
> Investigation & Diagnostic Centres - Wallaceville
> Biosecurity New
> Zealand Ministry of Agriculture and Forestry
>
> Phone 04 894 5600 Fax 04 894 4973 Mobile 029 894 5611
> Postal address:
> Investigation and Diagnostic Centre- Wallaceville Box 40742
> Ward St
> Upper Hutt
>
>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri 06 Jun 2008 - 05:36:01 GMT

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