Re: matrix question

["Dimitris Rizopoulos" <dimitris.rizopoulos@med.kuleuven.be>]

rle() is your friend in this case, i.e.,

mat1 <- apply(mat, 2, function(x) {
rl <- rle(x)
rep(rl$length, rl$lengths)
})

mat2 <- apply(mat, 2, function(x) {
rl <- rle(x)
unlist(lapply(rl$length, seq, from = 1))
})

where 'mat' is your original matrix.

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
    http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Eric yang" <yang_eric9@yahoo.com>
To: <s-news@wubios.wustl.edu>
Sent: Tuesday, March 07, 2006 12:11 PM
Subject: [S] matrix question


>  Dear members,
>
>  I have a simple matrix problem which is solvable using for-loops 
> but as they're not particular efficient I would prefer not to use 
> them.
>  Here is an example of what I'm trying to do. Suppose I have the 
> following matrix
>  >my.matrix
>          [,1]     [,2]     [,3]     [,4]     [,5]
> [1,] 19.35602 20.82310 18.71526 17.33000 20.71457
> [2,] 20.12000 21.12000 21.22000 17.33000 23.06444
> [3,] 20.12000 21.12000 21.22000 17.33000 21.34383
> [4,] 20.12000 21.12000 21.22000 17.33000 20.27115
> [5,] 20.12000 22.12000 21.22000 18.33000 20.03679
> [6,] 20.12000 22.12000 21.22000 18.33000 26.12412
> [7,] 20.12000 22.12000 21.22000 19.33000 19.84222
> [8,] 20.12000 23.12000 20.53322 19.33000 19.42392
> [9,] 20.12000 23.12000 18.52401 19.33000 21.56694
> [10,] 20.12000 23.12000 21.66532 20.37692 18.93681
> [11,] 20.12000 23.80764 18.67000 21.06952 21.97545
> [12,] 20.12000 21.67629 18.67000 20.33678 20.90008
> [13,] 20.12000 21.00464 18.67000 19.36164 18.38411
>
>  I want to create two additional matrices (or an array) related to 
> this one. The first matrix counts (column by column) the number of 
> consecutive repeatitions of a value for each column, i.e.
>   >my.matrix1
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    1    1    1    4    1
> [2,]   12    3    6    4    1
> [3,]   12    3    6    4    1
> [4,]   12    3    6    4    1
> [5,]   12    3    6    2    1
> [6,]   12    3    6    2    1
> [7,]   12    3    6    3    1
> [8,]   12    3    1    3    1
> [9,]   12    3    1    3    1
> [10,]   12    3    1    1    1
> [11,]   12    1    3    1    1
> [12,]   12    1    3    1    1
> [13,]   12    1    3    1    1
>
>  and the other matrix defines the repeatition number within the 
> sequence, i.e.
>   >my.matrix2
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    1    1    1    1    1
> [2,]    1    1    1    2    1
> [3,]    2    2    2    3    1
> [4,]    3    3    3    4    1
> [5,]    4    1    4    1    1
> [6,]    5    2    5    2    1
> [7,]    6    3    6    1    1
> [8,]    7    1    1    2    1
> [9,]    8    2    1    3    1
> [10,]    9    3    1    1    1
> [11,]   10    1    1    1    1
> [12,]   11    1    2    1    1
> [13,]   12    1    3    1    1
>
>  I would appreciate any help in constructing my.matrix1 and 
> my.matrix2 without the need for using for-loops.
>  Thanks in advance.
>
>  Regards
>
>  Eric
>
>
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