[R] intersect of list elements

[Berton Gunter]

FAQ 7.21.

But there are perhaps slicker ways.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Georg Otto
> Sent: Friday, July 21, 2006 10:39 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] intersect of list elements
> 
> 
> Hi,
> 
> i have a list of several vectors, for example:
> 
> > vectorlist
> $vector.a.1
> [1] "a" "b" "c"
> 
> $vector.a.2
> [1] "a" "b" "d"
> 
> $vector.b.1
> [1] "e" "f" "g"
> 
> 
> I can use intersect to find elements that appear in $vector.a.1 and
> $vector.a.2:
> 
> > intersect(vectorlist[[1]], vectorlist[[2]])
> [1] "a" "b"
> 
> 
> I would like to use grep to get the vectors by their names matching an
> expression and to find the intersects between those vectors. For the
> first step:
> 
> > vectorlist[grep ("vector.a", names(vectorlist))]
> $vector.a.1
> [1] "a" "b" "c"
> 
> $vector.a.2
> [1] "a" "b" "d"
> 
> 
> Unfortunately, I can not pass the two vectors as argument to 
> intersect:
> 
> > intersect(vectorlist[grep ("vector.a", names(vectorlist))])
> Error in unique(y[match(x, y, 0)]) : argument "y" is missing, 
> with no default
> 
> I am running R Version 2.3.1 (2006-06-01) 
> 
> 
> Could somone help me to solve this?
> 
> Cheers,
> 
> Georg
> 
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>