[R] Finding Equal Elements in Vectors
Marc Schwartz
MSchwartz at MedAnalytics.com
Sun Feb 27 16:50:07 CET 2005
After I hit send, I realized an error in:
> which(a %in% b)
[1] 8 9 10
The above should be:
> a[which(a %in% b)]
[1] 8 9 10
They happen to be the same by coincidence only, given the values that I
used.
The first syntax returns the _indices_ of the matches, not the actual
matched values themselves. Important difference.
For example and clarity:
> a <- 5:15
> b <- 12:20
> a
[1] 5 6 7 8 9 10 11 12 13 14 15
> b
[1] 12 13 14 15 16 17 18 19 20
> which(a %in% b)
[1] 8 9 10 11
> a[which(a %in% b)]
[1] 12 13 14 15
Sorry for the confusion.
Marc
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