Re: [R] almost lower triangular matrices

From: Rolf Turner <rolf_at_math.unb.ca>
Date: Wed 02 Mar 2005 - 07:24:50 EST

 > x <- 1:6 # In real life x <- scan(<filename>).
 > m <- matrix(0,4,4)
 > m[row(m)<col(m)] <- x
 > m <- t(m)
 > m
     [,1] [,2] [,3] [,4]
[1,]    0    0    0    0
[2,]    1    0    0    0

[3,] 2 3 0 0
[4,] 4 5 6 0

The fiddle with the transposing is needed because R puts data into matrices column-by-column, not row-by-row.

                                cheers,

					Rolf Turner
					rolf@math.unb.ca

Michael Anyadike-Danes wrote:

> I have output from a program which produces a distance matrix I want
> to read into a clustering program in R.
>
> The output is a .txt file and is 'almost' lower triangular in the
> sense that it is just the triangle below the diagonal.
>
> So for example a 4-by-4 distance matrix appears as,
>
> 1
>
> 2 3
>
> 4 5 6
>
> i.e. it looks like a lower triangular of a 3-by3.
>
> I thought I might be able to use "diag" to add zeros but apparently not.
>
> It's a problem because my matrix is actually 1989-by-1989 not 4-by-4
>
> I would not be at all surprised if the solution is obvious but I cannot
> quite see how to read this into R.



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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Mar 02 08:56:53 2005

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