Thanks Martin!




________________________________
From: Martin Morgan <mtmorgan@fhcrc.org>

Cc: r-help@r-project.org
Sent: Mon, March 14, 2011 12:33:40 PM
Subject: Re: [R] ideas on sorting

On 03/14/2011 10:32 AM, array chip wrote:
> Hi, I have a character vector as below:
>
> a<-c('10','3R','4','4R','5','5R','6','6R','7','8','9','7R','1','10R','11'
> ,'11R','12','12R','13','13R','14','14R','15','15R','1R','2','2R','3','8R'
> ,'9R')
>
> Is there a clever way to sort this easily to return a vector of index that 
>would
> produce a vector as below:
>
> a[index]:
>
>   [1] "1"   "2"   "3"   "4"   "5"   "6"   "7"   "8"   "9"   "10"
> [11] "11"  "12"  "13"  "14"  "15"  "1R"  "2R"  "3R"  "4R"  "5R"
> [21] "6R"  "7R"  "8R"  "9R"  "10R" "11R" "12R" "13R" "14R" "15R"

treat these as levels of a factor and let R do the thinking

   lvls = c(1:15, paste(1:15, "R", sep=""))
   a = factor(c('10', '3R', '4', '4R', '5', '5R', '6', '6R', '7', '8',
                '9', '7R', '1', '10R', '11', '11R', '12', '12R', '13',
                '13R', '14', '14R', '15', '15R', '1R', '2', '2R', '3',
                '8R' , '9R'), levels=lvls)

> sort(a)
  [1] 1   2   3   4   5   6   7   8   9   10  11  12  13  14
[15] 15  1R  2R  3R  4R  5R  6R  7R  8R  9R  10R 11R 12R 13R
[29] 14R 15R
30 Levels: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1R 2R ... 15R
> a[order(a)]
  [1] 1   2   3   4   5   6   7   8   9   10  11  12  13  14
[15] 15  1R  2R  3R  4R  5R  6R  7R  8R  9R  10R 11R 12R 13R
[29] 14R 15R
30 Levels: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1R 2R ... 15R


Martin


>
> Thanks,
>
> John
>
>
>
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>
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