Hello,
From the help page for
?`==`
Note
Do not use |==| and |!=| for tests, such as in |if| expressions, where
you must get a single |TRUE| or |FALSE|. Unless you are absolutely sure
that nothing unusual can happen, you should use the |identical
<http://127.0.0.1:16370/library/base/help/identical>| function instead.
inx <- sapply(a$y, identical, 0)
inx
[1] FALSE TRUE FALSE FALSE TRUE FALSE FALSE FALSE FALSE TRUE
a[inx, ]
x y
2 2 0
5 5 0
10 10 0
Or, I think better because it's simpler:
not.na <- !is.na(a$y)
a[not.na & a$y == 0, ]
x y
2 2 0
5 5 0
10 10 0
Hope this helps,
Rui Barradas
Em 15-08-2012 21:06, Robin Jeffries escreveu:
> Simply put, I want to subset the data frame 'a' where 'y=0'.
>
>> a <- as.data.frame(cbind(x=1:10, y=c(1,0,NA,1,0,NA,NA,1,1,0)))
>> a
> x y
> 1 1 1
> 2 2 0
> 3 3 NA
> 4 4 1
> 5 5 0
> 6 6 NA
> 7 7 NA
> 8 8 1
> 9 9 1
> 10 10 0
>
>> names(a)
> [1] "x" "y"
>
>> table(a$y)
> 0 1
> 3 4
>
>> table(a$y, useNA="always")
> 0 1 <NA>
> 3 4 3
>
>> b <- a[a$y==0,]
>> b
> x y
> 2 2 0
> NA NA NA
> 5 5 0
> NA.1 NA NA
> NA.2 NA NA
> 10 10 0
>
>> is(a$y)
> [1] "numeric" "vector"
>
>
> Instead of only pulling the rows where a$y==0, i'm getting where they're 0,
> OR NA. ? Again I feel like either something was changed when I wasn't
> looking.. or I'm reaaaaaaly forgetting something important.
>
> Thanks,
>
> Robin Jeffries
> MS, DrPH Candidate
> Department of Biostatistics,
> UCLA
> 530-633-STAT(7828)
> rjeffr...@ucla.edu
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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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.
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