[R] row-echelon form (was no subject)

[Spencer Graves]

How does this compare with R of the qr decomposition?  spencer graves

John Fox wrote:

>Dear Amin,
>
>I have a function (created just for demonstration, and reproduced below) for
>finding the row-echelon form of a matrix. I'm sure that many list members
>could produce something that's better numerically, but this should be OK at
>least for toy problems.
>
>John
>
>--------- snip -------------
>
>rowEchelonForm <- function(X, tol=.Machine$double.eps){
>    if ((!is.matrix(X)) || (!is.numeric(X))) stop("argument must be a
>numeric matrix")
>    Z <- X
>    for (i in 1:min(dim(X))){
>        if (i > 1) Z[i-1,] <- 0
>        which <- which.max(abs(Z[,i]))  # find maximum pivot in current
>column at or below current row
>        pivot <- X[which, i]
>        if (abs(pivot) <= tol) next     # check for 0 pivot
>        if (which > i) X[c(i,which),] <- X[c(which,i),]  # exchange rows
>        X[i,] <- X[i,]/pivot            # pivot
>        row <- X[i,]                    
>        X <- X - outer(X[,i], row)      # sweep
>        X[i,] <- row                    # restore current row
>        }
>    n <- nrow(X)
>    for (i in 1:n) if (max(abs(X[i,])) <= tol) X[c(i,n),] <- X[c(n,i),]   #
>0 rows to bottom
>    X
>    }
>        
>
>  
>
>>-----Original Message-----
>>From: r-help-bounces at stat.math.ethz.ch 
>>[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Aimin Yan
>>Sent: Wednesday, March 03, 2004 2:42 PM
>>To: r-help at stat.math.ethz.ch
>>Subject: [R] (no subject)
>>
>>how to produce a  Row Reduced Echelon Form for a matrix in R?
>>Aimin Yan
>>
>>______________________________________________
>>R-help at stat.math.ethz.ch mailing list
>>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
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>>http://www.R-project.org/posting-guide.html
>>    
>>
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
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>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>  
>