Re: Convert a Matrix of Indices to a Matrix of Values

["Liaw, Andy" <andy_liaw@merck.com>]

This is in R, but should be the same in S-PLUS:

 

> m <- matrix(sample(1:5, 20, replace=T), 5, 4)
> m
     [,1] [,2] [,3] [,4]
[1,]    3    4    2    2
[2,]    1    2    2    2
[3,]    1    4    2    5
[4,]    4    4    1    3
[5,]    5    1    1    2
> V <- v[m]
> dim(V) <- dim(m)
> V
     [,1] [,2] [,3] [,4]
[1,] "c"  "d"  "b"  "b"
[2,] "a"  "b"  "b"  "b"
[3,] "a"  "d"  "b"  "e"
[4,] "d"  "d"  "a"  "c"
[5,] "e"  "a"  "a"  "b"

Andy

---

From: s-news-owner@lists.biostat.wustl.edu on behalf of Paul H. Lasky
Sent: Thu 3/27/2008 10:52 AM
To: s-news@lists.biostat.wustl.edu
Subject: [S] Convert a Matrix of Indices to a Matrix of Values

 I have m vectors v with different lengths, and a n X m matrix of indices.
I wish to transform the index matrix to a matrix of values of v, with each column representing values of v.

  Can this transformation be accomplished without looping ? Using loops
the transformation is straightforward, awkward, and time consuming.

  Paul H. Lasky
  P & B Consulting
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