which() in subset()

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)

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