Hi I have a list. Two of the elements of this list are "Name" and "Address", both of which are character vectors. Name and Address are linked, so that the same "Name" always associates with the same "Address". What I want to do is pull out the unique values, as a new list of the same format (ie two elements of character vectors). Now I've worked out that unique(list$Name) will give me a list of the unique names, but how do I then go and link those to the correct (unique) addresses so I end up with a new list which is the same format as the rest, but now unique? Cheers Mick
On Wed, 1 Sep 2004, michael watson (IAH-C) wrote:> I have a list. Two of the elements of this list are "Name" and > "Address", both of which are character vectors. Name and Address are > linked, so that the same "Name" always associates with the same > "Address". > > What I want to do is pull out the unique values, as a new list of the > same format (ie two elements of character vectors). Now I've worked out > that unique(list$Name) will give me a list of the unique names, but how > do I then go and link those to the correct (unique) addresses so I end > up with a new list which is the same format as the rest, but now unique?match, as in match(unique(list$Name), list$name), OR indexing as in Address <- list$Address names(Address) <- list$Name Name <- unique(list$Name) list(Name, as.vector(Address[Name]) OR choose a better data structure as in unique(as.data.frame(list)) -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
Try this:
l.1 <- list(list(name='a', addr='123'),list(name='b',
addr='234'),
list(name='b', addr='234'), list(name='a',
addr='123')) # create a
list
l.names <- unlist(lapply(l.1, '[[', 'name')) # get the
'name'
l.u <- unique(l.names) # make unique
new.list <- l.1[match(l.u, l.names)] # create new list with just one
'name'
__________________________________________________________
James Holtman "What is the problem you are trying to solve?"
Executive Technical Consultant -- Office of Technology, Convergys
james.holtman at convergys.com
+1 (513) 723-2929
"michael watson
(IAH-C)" To: <R-help at
stat.math.ethz.ch>
<michael.watson at bbsrc cc:
.ac.uk> Subject: [R] Unique lists
from a list
Sent by:
r-help-bounces at stat.m
ath.ethz.ch
09/01/2004 10:31
Hi
I have a list. Two of the elements of this list are "Name" and
"Address", both of which are character vectors. Name and Address are
linked, so that the same "Name" always associates with the same
"Address".
What I want to do is pull out the unique values, as a new list of the
same format (ie two elements of character vectors). Now I've worked out
that unique(list$Name) will give me a list of the unique names, but how
do I then go and link those to the correct (unique) addresses so I end
up with a new list which is the same format as the rest, but now unique?
Cheers
Mick
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name <- c("a", "b", "a", "c",
"d", "a", "b")
addr <- c(10, 20, 10, 30, 40, 10, 20)
duplicated(name)
[1] FALSE FALSE TRUE FALSE FALSE TRUE TRUE
which(duplicated(name))
[1] 3 6 7
addr[ -which(duplicated(name)) ]
[1] 10 20 30 40
cbind( name, addr) [ -which(duplicated(name)), ]
name addr
[1,] "a" "10"
[2,] "b" "20"
[3,] "c" "30"
[4,] "d" "40"
Make sure that person named "a" always lives in address "10"
(i.e.
one-to-one mapping).
If it is possible for person "a" to have two addresses (e.g. house and
office) "10" and "11", then it might be better to collect
both address.
In this case, you can try :
addr2 <- c(10, 20, 11, 30, 40, 12, 21)
tapply(addr2, as.factor(name), function(x) paste(x, collapse=", ") )
a b c d
"10, 11, 12" "20, 21" "30"
"40"
To convert this into a list, use sapply(a, strsplit, split=", ").
On Wed, 2004-09-01 at 15:31, michael watson (IAH-C)
wrote:> Hi
>
> I have a list. Two of the elements of this list are "Name" and
> "Address", both of which are character vectors. Name and Address
are
> linked, so that the same "Name" always associates with the same
> "Address".
>
> What I want to do is pull out the unique values, as a new list of the
> same format (ie two elements of character vectors). Now I've worked
out
> that unique(list$Name) will give me a list of the unique names, but how
> do I then go and link those to the correct (unique) addresses so I end
> up with a new list which is the same format as the rest, but now unique?
>
> Cheers
> Mick
>
> ______________________________________________
> 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
>