which() in subset()

[Charles Stangor]

Why does the subset not work in the which() version below?

Thank you


v1 <- subset(t1,
 version_1==as.character("100-1")
 | version_1==as.character("100-2"))

a<-c("100-1", "100-2")
v1 <- subset(t1, which(a==as.character(version_1)) != 0)

        [[alternative HTML version deleted]]

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[Rui Barradas]

Hello,

To know why, just evaluate the condition, with 't1$' before 'version_1':

which(as.character(t1$version_1) %in% a) != 0
[1] TRUE TRUE


It allways evaluates to TRUE, therefore, subset() returns all rows.

See if this isn't simpler than both of your forms.

v2 <- subset(t1, version_1 %in% a)
v2
   id version_1
1  1     100-1
2  2     100-2

The trick is to use %in% when doing multiple comparisons. With the
vector with length equal to the number of observations on the left hand
side.

Hope this helps,

Rui Barradas

Em 13-07-2012 12:12, Charles Stangor escreveu:

> Why does the subset not work in the which() version below?
>
> Thank you
>
>
> v1 <- subset(t1,
>   version_1==as.character("100-1")
>   | version_1==as.character("100-2"))
>
> a<-c("100-1", "100-2")
> v1 <- subset(t1, which(a==as.character(version_1)) != 0)
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list
> 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.
>

______________________________________________
[hidden email] mailing list
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.

[Charles Stangor]

Thanks Dennis and Mike... I'm getting it!!!

Sent from my Android

Rui Barradas <[hidden email]> wrote:

>Hello,
>
>To know why, just evaluate the condition, with 't1$' before 'version_1':
>
>which(as.character(t1$version_1) %in% a) != 0
>[1] TRUE TRUE
>
>
>It allways evaluates to TRUE, therefore, subset() returns all rows.
>
>See if this isn't simpler than both of your forms.
>
>v2 <- subset(t1, version_1 %in% a)
>v2
>   id version_1
>1  1     100-1
>2  2     100-2
>
>The trick is to use %in% when doing multiple comparisons. With the
>vector with length equal to the number of observations on the left hand
>side.
>
>Hope this helps,
>
>Rui Barradas
>
>Em 13-07-2012 12:12, Charles Stangor escreveu:
>> Why does the subset not work in the which() version below?
>>
>> Thank you
>>
>>
>> v1 <- subset(t1,
>>   version_1==as.character("100-1")
>>   | version_1==as.character("100-2"))
>>
>> a<-c("100-1", "100-2")
>> v1 <- subset(t1, which(a==as.character(version_1)) != 0)
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> [hidden email] mailing list
>> 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.
>>
>

______________________________________________
[hidden email] mailing list
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.