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Georg Otto

2006-Jul-21 17:39 UTC

[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

Berton Gunter

2006-Jul-21 17:55 UTC

head link

[R] intersect of list elements

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.
>

Sundar Dorai-Raj

2006-Jul-21 18:02 UTC

head link

[R] intersect of list elements

Georg Otto wrote:> 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.

Will this work for you?

vectorlist <- list(vector.a.1 = c("a", "b",
"c"),
                    vector.a.2 = c("a", "b", "d"),
                    vector.b.1 = c("e", "f", "g"))

intersect2 <- function(...) {
   args <- list(...)
   nargs <- length(args)
   if(nargs <= 1) {
     if(nargs == 1 && is.list(args[[1]])) {
       do.call("intersect2", args[[1]])
     } else {
       stop("cannot evaluate intersection fewer than 2 arguments")
     }
   } else if(nargs == 2) {
     intersect(args[[1]], args[[2]])
   } else {
     intersect(args[[1]], intersect2(args[-1]))
   }
}

vector.a <- vectorlist[grep ("vector.a", names(vectorlist))]
intersect2(vector.a)
intersect2(vectorlist)

HTH,

--sundar

Gabor Grothendieck

2006-Jul-21 18:18 UTC

head link

[R] intersect of list elements

The following assumes that within each component of vectorlist
the vector elements are unique. In that case the first two lines
define vectorlist and perform the grep, as in your post.  Elements
of the intersection must occur n times where n is the number
of components of vectorlist that match the grep and those
elements are extracted in the last line.

# from your post
vectorlist <- list(vector.a.1 = c("a", "b",
"c"), vector.a.2 = c("a",
   "b", "d"), vector.b.1. = c("e", "f",
"g"))
idx <- grep("vector.a", names(vectorlist))

# get intersection
names(which(table(unlist(vectorlist[idx])) == length(idx)))

On 7/21/06, Georg Otto <georg.otto at tuebingen.mpg.de>
wrote:>
> 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.
>

R help - Jul 2006 - intersect of list elements

[R] intersect of list elements

[R] intersect of list elements

[R] intersect of list elements

[R] intersect of list elements