Because I didn't find in R any functions similar to the function 'reduce' from
Python, I'm writing a function "freduce" as follows:
freduce <- function(f, vec, ValIni=NULL, StopIn=NULL) {
# f: is any function that takes two arguments of the same type
# vec: is a vector of n values accepted by 'f'
#
# Initially f starts with ValIni, if it's given or the first element
# of 'vec', and then applies sequentially f to that value and one of the
# elements of 'vec', leaving the result as the first argument of 'f' for
# the next application of the function.
#
# If StopIN is given, the result is compared with this value to stop the
# operation and return such a value.
# Detects if ValIni was given:
r <- if (is.null(ValIni)) c(2,vec[1]) else c(1,ValIni)
for (e in vec[r[1]:length(vec)]) {
if (!is.null(StopIn) && r[2] == StopIn) return (StopIn)
r[2] <- do.call(f, list(r[2],e))
}
return(r[2])
}
When this function is called with '+' and a vector of numbers, it behaves
exactly as sum
* freduce('+', c(3.5, 2.7, -1))
[1] 5.2
* sum(c(3.5, 2.7, -1))
[1] 5.2
But, then, you can call it with other operators; for instance, a generalized
'or' or 'and' operation, optionally stoping the operation when the value is
determined:
* freduce('|', c(0,0,1,0,0,1), StopIn=T)
[1] TRUE
* freduce('&', c(0,0,1,0,0,1), StopIn=F)
[1] FALSE
My question is if there exists a way to do this more directly in R?
Thanks,
--Sergio.
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