R help - Apr 2011 - Counting elements in columns

I have two columns and I want to count hwo many pairs I have of the same
element. For example. If I have
a = c(1,2,3,4,5)
b= c(12, 1, 34, 2, 5, 0, 10, 100, 11)
It should return 3 (since 1, 2 and 5 occur in both columns).
Columns need not be of the same length.

-- 
Thanks,
Jim.

	[[alternative HTML version deleted]]

length(intersect(a, b))


On Sat, Apr 16, 2011 at 8:04 PM, Jim Silverton <jim.silverton at
gmail.com> wrote:
> I have two columns and I want to count hwo many pairs I have of the same
> element. For example. If I have
> a = c(1,2,3,4,5)
> b= c(12, 1, 34, 2, 5, 0, 10, 100, 11)
> It should return 3 (since 1, 2 and 5 occur in both columns).
> Columns need not be of the same length.
>
> --
> Thanks,
> Jim.
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org 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.
>

Hi,
try this;

sum(sapply(a, function(x) (x==b)))

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