# a question on list manipulation

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## a question on list manipulation

 Hi R users, I have a list: > x \$A [1] "a"  "b"  "c" \$B [1] "b"  "c" \$C [1] "c" I want to convert it to a lowercase-to-uppercase list like this: > y \$a [1] "A" \$b [1] "A"  "B" \$c [1] "A"  "B"  "C" In a word, I want to reverse the list names and the elements under each list name. Is there any quick way to do that? Thanks -- Best, Zhenjiang ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 There are a few moving pieces to do this: 1) the toupper and tolower functions. These can do almost everything you need: x = lapply(x,toupper) ## This changes the things inside x but won't change the names 2) Now, there are two ways to think about getting the elements from one list to another: I'd prefer think about changing the list names and order while leaving the elements in the lists (as for big data it will be more memory efficient) but you could work on actually moving things. Here it's easy: first reverse x = rev(x) now you have the problem that "c" is the first element of the list so you just need to reverse the whole list and you might as well make them lowercase while you are at it names(x) = tolower(names(x)[3:1]) # 3:1 will reorder the list, use length(x) more generally Altogether, x = rev(lapply(x,toupper)) names(x) = tolower(names(x)[3:1]) gives us >x \$a [1] "C" \$b [1] "B" "C" \$c [1] "A" "B" "C" as desired. By the way, this is a very odd request: are you sure this is really what you need to do? If you describe the more general framework, we can probably help with some more efficient data management. Hope this helps, Michael Weylandt On Fri, Aug 5, 2011 at 12:05 PM, zhenjiang xu <[hidden email]>wrote: > Hi R users, > > I have a list: > > x > \$A > [1] "a"  "b"  "c" > \$B > [1] "b"  "c" > \$C > [1] "c" > > I want to convert it to a lowercase-to-uppercase list like this: > > y > \$a > [1] "A" > \$b > [1] "A"  "B" > \$c > [1] "A"  "B"  "C" > > In a word, I want to reverse the list names and the elements under > each list name. Is there any quick way to do that? Thanks > -- > Best, > Zhenjiang > > ______________________________________________ > [hidden email] 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. >         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 In reply to this post by zhenjiang xu On Aug 5, 2011, at 12:05 PM, zhenjiang xu wrote: > Hi R users, > > I have a list: >> x > \$A > [1] "a"  "b"  "c" > \$B > [1] "b"  "c" > \$C > [1] "c" > > I want to convert it to a lowercase-to-uppercase list like this: >> y > \$a > [1] "A" > \$b > [1] "A"  "B" > \$c > [1] "A"  "B"  "C" > > In a word, I want to reverse the list names and the elements under > each list name. Is there any quick way to do that? Thanks The obvious way would be: names(lll) <- to.upper(names(lll) lll <- lapply(lll, to.lower) (If you had offered code that would construct the list, I would have   tested it.) -- David Winsemius, MD West Hartford, CT ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 In reply to this post by zhenjiang xu toupper()/tolower() are the functions to convert the letters. lapply() can be used to apply this to different list elements and names() is helpfull to convert the names of your list. HTH Jannis On 08/05/2011 06:05 PM, zhenjiang xu wrote: > Hi R users, > > I have a list: >> x > \$A > [1] "a"  "b"  "c" > \$B > [1] "b"  "c" > \$C > [1] "c" > > I want to convert it to a lowercase-to-uppercase list like this: >> y > \$a > [1] "A" > \$b > [1] "A"  "B" > \$c > [1] "A"  "B"  "C" > > In a word, I want to reverse the list names and the elements under > each list name. Is there any quick way to do that? Thanks ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 In reply to this post by zhenjiang xu On 05/08/2011 12:05 PM, zhenjiang xu wrote: > Hi R users, > > I have a list: > >  x > \$A > [1] "a"  "b"  "c" > \$B > [1] "b"  "c" > \$C > [1] "c" > > I want to convert it to a lowercase-to-uppercase list like this: > >  y > \$a > [1] "A" > \$b > [1] "A"  "B" > \$c > [1] "A"  "B"  "C" > > In a word, I want to reverse the list names and the elements under > each list name. Is there any quick way to do that? Thanks I interpreted this question differently from the others, and your example is ambiguous as to which is the right interpretation.  I thought you wanted to swap names and elements,  so  > x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d"))  > x \$A [1] "d" "e" "f" \$B [1] "d" "e" \$C [1] "d" would become  > list(d=c("A", "B", "C"), e=c("A", "B"), f="A") \$d [1] "A" "B" "C" \$e [1] "A" "B" \$f [1] "A" I don't know a slick way to do this; I'd just do it by brute force, looping over the names of x. Duncan Murdoch ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 Exactly! Sorry I get others misunderstood. The uppercase/lowercase is only a toy example (and a bad one; yours is better than mine). My question is a more general one: a list is basically a one-to-many matching, from the names of a list to the elements belonging to each name. I'd like to reverse the matching, from all the elements to the names of the list. On Fri, Aug 5, 2011 at 12:53 PM, Duncan Murdoch <[hidden email]> wrote: > On 05/08/2011 12:05 PM, zhenjiang xu wrote: >> >> Hi R users, >> >> I have a list: >> >  x >> \$A >> [1] "a"  "b"  "c" >> \$B >> [1] "b"  "c" >> \$C >> [1] "c" >> >> I want to convert it to a lowercase-to-uppercase list like this: >> >  y >> \$a >> [1] "A" >> \$b >> [1] "A"  "B" >> \$c >> [1] "A"  "B"  "C" >> >> In a word, I want to reverse the list names and the elements under >> each list name. Is there any quick way to do that? Thanks > > I interpreted this question differently from the others, and your example is > ambiguous as to which is the right interpretation.  I thought you wanted to > swap names and elements,  so > >> x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) >> x > \$A > [1] "d" "e" "f" > > \$B > [1] "d" "e" > > \$C > [1] "d" > > would become > >> list(d=c("A", "B", "C"), e=c("A", "B"), f="A") > \$d > [1] "A" "B" "C" > > \$e > [1] "A" "B" > > \$f > [1] "A" > > I don't know a slick way to do this; I'd just do it by brute force, looping > over the names of x. > > Duncan Murdoch > -- Best, Zhenjiang ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 Hi: Your clarification suggests Duncan was on the right track, so how about this: x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) x2 <- unique(unlist(x)) w <- lapply(x, function(u) names(x)[which(x2 %in% u)]) names(w) <- x2 w \$d [1] "A" "B" "C" \$e [1] "A" "B" \$f [1] "A" HTH, Dennis On Fri, Aug 5, 2011 at 10:04 AM, zhenjiang xu <[hidden email]> wrote: > Exactly! Sorry I get others misunderstood. The uppercase/lowercase is > only a toy example (and a bad one; yours is better than mine). My > question is a more general one: a list is basically a one-to-many > matching, from the names of a list to the elements belonging to each > name. I'd like to reverse the matching, from all the elements to the > names of the list. > > On Fri, Aug 5, 2011 at 12:53 PM, Duncan Murdoch > <[hidden email]> wrote: >> On 05/08/2011 12:05 PM, zhenjiang xu wrote: >>> >>> Hi R users, >>> >>> I have a list: >>> >  x >>> \$A >>> [1] "a"  "b"  "c" >>> \$B >>> [1] "b"  "c" >>> \$C >>> [1] "c" >>> >>> I want to convert it to a lowercase-to-uppercase list like this: >>> >  y >>> \$a >>> [1] "A" >>> \$b >>> [1] "A"  "B" >>> \$c >>> [1] "A"  "B"  "C" >>> >>> In a word, I want to reverse the list names and the elements under >>> each list name. Is there any quick way to do that? Thanks >> >> I interpreted this question differently from the others, and your example is >> ambiguous as to which is the right interpretation.  I thought you wanted to >> swap names and elements,  so >> >>> x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) >>> x >> \$A >> [1] "d" "e" "f" >> >> \$B >> [1] "d" "e" >> >> \$C >> [1] "d" >> >> would become >> >>> list(d=c("A", "B", "C"), e=c("A", "B"), f="A") >> \$d >> [1] "A" "B" "C" >> >> \$e >> [1] "A" "B" >> >> \$f >> [1] "A" >> >> I don't know a slick way to do this; I'd just do it by brute force, looping >> over the names of x. >> >> Duncan Murdoch >> > > > > -- > Best, > Zhenjiang > > ______________________________________________ > [hidden email] 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. > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 In reply to this post by zhenjiang xu Here is one approach, whether it is better than the basic loop or not is up to you: > x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) > > tmp <- unlist(x) > tmp2 <- sub( '[0-9]+\$', '', names(tmp) ) > > x.new <- split( tmp2, tmp ) > x.new \$d [1] "A" "B" "C" \$e [1] "A" "B" \$f [1] "A" Of course this version will have some problems if the names of your list elements end with digits that you don't want stripped off (but you can work around that by preprocessing the list names). -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [hidden email] 801.408.8111 > -----Original Message----- > From: [hidden email] [mailto:r-help-bounces@r- > project.org] On Behalf Of zhenjiang xu > Sent: Friday, August 05, 2011 11:04 AM > To: Duncan Murdoch > Cc: r-help > Subject: Re: [R] a question on list manipulation > > Exactly! Sorry I get others misunderstood. The uppercase/lowercase is > only a toy example (and a bad one; yours is better than mine). My > question is a more general one: a list is basically a one-to-many > matching, from the names of a list to the elements belonging to each > name. I'd like to reverse the matching, from all the elements to the > names of the list. > > On Fri, Aug 5, 2011 at 12:53 PM, Duncan Murdoch > <[hidden email]> wrote: > > On 05/08/2011 12:05 PM, zhenjiang xu wrote: > >> > >> Hi R users, > >> > >> I have a list: > >> >  x > >> \$A > >> [1] "a"  "b"  "c" > >> \$B > >> [1] "b"  "c" > >> \$C > >> [1] "c" > >> > >> I want to convert it to a lowercase-to-uppercase list like this: > >> >  y > >> \$a > >> [1] "A" > >> \$b > >> [1] "A"  "B" > >> \$c > >> [1] "A"  "B"  "C" > >> > >> In a word, I want to reverse the list names and the elements under > >> each list name. Is there any quick way to do that? Thanks > > > > I interpreted this question differently from the others, and your > example is > > ambiguous as to which is the right interpretation.  I thought you > wanted to > > swap names and elements,  so > > > >> x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) > >> x > > \$A > > [1] "d" "e" "f" > > > > \$B > > [1] "d" "e" > > > > \$C > > [1] "d" > > > > would become > > > >> list(d=c("A", "B", "C"), e=c("A", "B"), f="A") > > \$d > > [1] "A" "B" "C" > > > > \$e > > [1] "A" "B" > > > > \$f > > [1] "A" > > > > I don't know a slick way to do this; I'd just do it by brute force, > looping > > over the names of x. > > > > Duncan Murdoch > > > > > > -- > Best, > Zhenjiang > > ______________________________________________ > [hidden email] 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. ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: a question on list manipulation

 In reply to this post by djmuseR This is a nice solution. Thanks, Dennis. But I am afraid if the length of the list x isn't equal to the length of x2, there will be errors since lapply returns a list of the same length. > x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d","g")) > x2 <- unique(unlist(x)) > w <- lapply(x, function(u) names(x)[which(x2 %in% u)]) > names(w) <- x2 Error in names(w) <- x2 :   'names' attribute [4] must be the same length as the vector [3] On Fri, Aug 5, 2011 at 3:23 PM, Dennis Murphy <[hidden email]> wrote: > Hi: > > Your clarification suggests Duncan was on the right track, so how about this: > > x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) > x2 <- unique(unlist(x)) > w <- lapply(x, function(u) names(x)[which(x2 %in% u)]) > names(w) <- x2 > w > \$d > [1] "A" "B" "C" > > \$e > [1] "A" "B" > > \$f > [1] "A" > > HTH, > Dennis > > On Fri, Aug 5, 2011 at 10:04 AM, zhenjiang xu <[hidden email]> wrote: >> Exactly! Sorry I get others misunderstood. The uppercase/lowercase is >> only a toy example (and a bad one; yours is better than mine). My >> question is a more general one: a list is basically a one-to-many >> matching, from the names of a list to the elements belonging to each >> name. I'd like to reverse the matching, from all the elements to the >> names of the list. >> >> On Fri, Aug 5, 2011 at 12:53 PM, Duncan Murdoch >> <[hidden email]> wrote: >>> On 05/08/2011 12:05 PM, zhenjiang xu wrote: >>>> >>>> Hi R users, >>>> >>>> I have a list: >>>> >  x >>>> \$A >>>> [1] "a"  "b"  "c" >>>> \$B >>>> [1] "b"  "c" >>>> \$C >>>> [1] "c" >>>> >>>> I want to convert it to a lowercase-to-uppercase list like this: >>>> >  y >>>> \$a >>>> [1] "A" >>>> \$b >>>> [1] "A"  "B" >>>> \$c >>>> [1] "A"  "B"  "C" >>>> >>>> In a word, I want to reverse the list names and the elements under >>>> each list name. Is there any quick way to do that? Thanks >>> >>> I interpreted this question differently from the others, and your example is >>> ambiguous as to which is the right interpretation.  I thought you wanted to >>> swap names and elements,  so >>> >>>> x <- list(A=c("d", "e", "f"), B=c("d", "e"), C=c("d")) >>>> x >>> \$A >>> [1] "d" "e" "f" >>> >>> \$B >>> [1] "d" "e" >>> >>> \$C >>> [1] "d" >>> >>> would become >>> >>>> list(d=c("A", "B", "C"), e=c("A", "B"), f="A") >>> \$d >>> [1] "A" "B" "C" >>> >>> \$e >>> [1] "A" "B" >>> >>> \$f >>> [1] "A" >>> >>> I don't know a slick way to do this; I'd just do it by brute force, looping >>> over the names of x. >>> >>> Duncan Murdoch >>> >> >> >> >> -- >> Best, >> Zhenjiang >> >> ______________________________________________ >> [hidden email] 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. >> > -- Best, Zhenjiang ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.