Debugging

Our assignment this week was to find a bug in a function with deliberate bugs.

The function was

tukey_multiple <- function(x) { 
   outliers <- array(TRUE,dim=dim(x)) 
   for (j in 1:ncol(x)) 
    { 
    outliers[,j] <- outliers[,j] && tukey.outlier(x[,j]) 
    } 
outlier.vec <- vector(length=nrow(x)) 
    for (i in 1:nrow(x))     { outlier.vec[i] <- all(outliers[i,]) } return(outlier.vec) }


Running it as such reports an error in

Error: unexpected symbol in:
"for (i in 1:nrow(x))
{ outlier.vec[i] <- all(outliers[i,]) } return"

I restructured the last few lines so they more closely matched the top

tukey_multiple <- function(x) { 
  outliers <- array(TRUE,dim=dim(x)) 
  for (j in 1:ncol(x)) 
  { 
    outliers[,j] <- outliers[,j] && tukey.outlier(x[,j]) 
  } 
  outlier.vec <- vector(length=nrow(x)) 
  for (i in 1:nrow(x)) 
  { 
    outlier.vec[i] <- all(outliers[i,]) 
  } 
  return(outlier.vec) 
}

The function then was properly created. However, when applying it to a matrix

tukey_multiple(matrix( rnorm(5*5,mean=0,sd=1), 5, 5))
Error: could not find function "tukey.outlier"

tukey.outlier isn't actually a function. I'm not sure if this was deliberate, or if it's wrapped up in a package I don't have. Google didn't reveal anything useful for a search on "tukey.outlier R". So I proceeded to use some of R's debugging.

> debug(tukey_multiple)
> tukey_multiple(matrix( rnorm(5*5,mean=0,sd=1), 5, 5))
debugging in: tukey_multiple(matrix(rnorm(5 * 5, mean = 0, sd = 1), 5, 5))
debug at #1: {
    outliers <- array(TRUE, dim = dim(x))
    for (j in 1:ncol(x)) {
        outliers[, j] <- outliers[, j] && tukey.outlier(x[, j])
    }
    outlier.vec <- vector(length = nrow(x))
    for (i in 1:nrow(x)) {
        outlier.vec[i] <- all(outliers[i, ])
    }
    return(outlier.vec)
}
Browse[2]>

Not sure why mine says Browse[2] and the lecture does Browse[1], and I'm not totally certain how to proceed from here. However, if this missing function was found it seems the function should work.