[R] count frequency

[Rainer M Krug]

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On 17/09/10 14:19, Alaios wrote:
> Hello everyone,
> please consider the following lines of a matrix
> 
> 
> [574,]   59   32
> [575,]   59   32
> [576,]   59   32
> [577,]   59   32
> [578,]   59   32
> [579,]   59   32
> [580,]   59   32
> [581,]   60   32
> [582,]   60   33
> [583,]   60   33
> [584,]   60   33
> [585,]   60   33
> [586,]   60   33
> [587,]   60   33
> [588,]   60   33
> [589,]   60   33
> [590,]   60   33
> [591,]   61   33
> [592,]   61   33
> [593,]   61   33
> [594,]   61   33
> [595,]   61   33
> [596,]   61   33
> [597,]   61   33
> [598,]   61   33
> [599,]   61   33
> [600,]   61   33
> [601,]   62   34
> 
> Is it possible somehow to count the similarities between the first and second 
> column and put them on a third column like this?
> 
> 59 32 3
> 60 33 5
> 62 34 1
> 
> where (3,5,1 are the frequencies for (59,32), (60,33) and (62,34)

One solution:

> x <- data.frame(a=trunc(runif(10)*10), b=trunc(runif(10)*10))
> x
   a b
1  6 5
2  7 5
3  1 5
4  0 4
5  3 9
6  6 8
7  4 3
8  0 4
9  2 7
10 7 2
> x$comb <- paste(x$a, x$b)
> x
   a b comb
1  6 5  6 5
2  7 5  7 5
3  1 5  1 5
4  0 4  0 4
5  3 9  3 9
6  6 8  6 8
7  4 3  4 3
8  0 4  0 4
9  2 7  2 7
10 7 2  7 2
> table(x$comb)

0 4 1 5 2 7 3 9 4 3 6 5 6 8 7 2 7 5
  2   1   1   1   1   1   1   1   1
>

I am sure, there are better ones

Cheers,

Rainer

> 
> Best Regards
> Alex
> 
> 
> 
>       
> 	[[alternative HTML version deleted]]
> 
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> and provide commented, minimal, self-contained, reproducible code.


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Natural Sciences Building
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