CODEWITHSUNDEEP
rfunction
fabla
fabla

Reputation: 1816

Recreating the diag() function

I am currently trying to duplicate the diag() function in R to get a better understanding. Unfortunately, my solution is only useful for symmetric matrices.

diagnew <- function(x){
  k <- c()
  for(i in 1:nrow(x)){
    k[i] <- x[i,i]
  }
  return(k)
}

I would be grateful for any tips that allow me to generalize my function.

Upvotes: 3

Views: 123

Answers (1)

Rui Barradas
Rui Barradas

Reputation: 76605

The error comes from looping pass min(nrow, ncol).

diagnew <- function(x){
  n <- min(nrow(x), ncol(x))
  k <- vector(class(x[1,1]), n)
  for(i in seq.int(n)){
    k[i] <- x[i,i]
  }
  k
}

mat <- matrix(1:10, 5)
diag(mat)
diagnew(mat)

identical(diag(mat), diagnew(mat))
#[1] TRUE

Upvotes: 3

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