[R] factor manipulation: edgelist to a matrix?

[Dimitris Rizopoulos]

one way is the following:

V1 <- c(1,1,1,2,3,3,3,3)
V2 <- LETTERS[c(1,1,2,1,3,1,3,2)]

tab <- table(V1, ave(V1, V1, FUN = seq_along))
vals <- as.vector(t(tab))
vals[vals != 0] <- unlist(split(V2, V1))
vals[vals == 0] <- NA
matrix(vals, nrow(tab), ncol(tab), TRUE)


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://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Christopher Marcum" <cmarcum at uci.edu>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, December 20, 2007 8:33 AM
Subject: [R] factor manipulation: edgelist to a matrix?


> Hello All,
>
> I have had considerable bad luck with attempting the following with 
> for
> loops. Here is the problem:
>
>
> # Suppose we have a data.frame with the following data, which can be
> considered a type of edgelist (for those with networks backgrounds):
> #
> #       V1 V2
> # 1 A
> # 1 A
> # 1 B
> # 2 A
> # 3 C
> # 3 A
> # 3 C
> # 3 B
> #
> # I want the output of the function to produce a matrix, such that 
> #each
> factor of V1 is a row, and each corresponding value at position k of 
> V2 is
> the i,j^th element of the new matrix, with missing values otherwise. 
> The
> desired output should be:
> # [,1] [,2] [,3] [,4]
> # [1,] A A B NA
> # [2,] A NA NA NA
> # [3,] C A C B
>
> I have explored the reshape package as well as the network package 
> in this
> pursuit, with no luck.
>
> Thanks,
> Chris Marcum
> UCI Sociology
>
> ______________________________________________
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> 


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