  # Matrix Row Echelon Form in R

For reasons unknown, I can’t find a function to transform a matrix into row echelon form in R. There’s a function on Rosetta Code for reduced row echelon form in R. So I wrote this on Sunday. And if you look at this and the Rosetta Code solution, they work in mostly the same way. This will be released as part of a larger package later, with documentation and unit tests. But it’s useful enough to stand on its own here.

```refmatrix <- function(m) {
count.rows <- nrow(m)
count.cols <- ncol(m)
piv <- 1

for(row.curr in 1:count.rows) {
if(count.cols > piv) {
i <- row.curr
while(m[i, piv] == 0) {
i <- i + 1
if(count.rows == i) {
i <- row.curr
piv <- piv + 1
if(count.cols == piv)
return(m)
}
}
m <- swaprows(m, row.curr, i)
for(j in row.curr:count.rows)
if(j != row.curr) {
k <- m[j, piv] / m[row.curr, piv]
m <- replacerow(m, row.curr, j, k)
}
piv <- piv + 1
}
}
return(m)
}

swaprows <- function(m, row1, row2) {
row.tmp <- m[row1,]
m[row1,] <- m[row2,]
m[row2,] <- row.tmp

return(m)
}

replacerow <- function(m, row1, row2, k) {
m[row2,] <- m[row2,] - m[row1,] * k
return(m)
}
```

Image by Frédérique Voisin-Demery.