`equal` function could be cleaner

[taylorokonek]

In termTraverse.R (soon to be in regress_utils.R), there is a function defined called equal, and the value returned calls the function itself (not sure if there are any implications to this?). The function seems to be doing the same thing as checking if length(unique(x)) == 1, other than that they would handle vectors that include NAs differently. This is mostly a reminder to myself to edit this helper function to be a bit cleaner in the future.

equal <- function(x){
if(length(x)==1){
return(TRUE)
} else {
if(x[1]!=x[2]){
return(FALSE)
} else {
return(equal(x[-1]))
}
}
}