Addition involving numeric(0) values

问题

Suppose x is a real number, or a vector. i is valued-False. Then x[i] will return numeric(0). I would like to treat this as a real number 0, or integer 0, which are both fit for addition.

numeric(0) added to any real number will return numeric(0), whereas I wish to obtain the real number being added as the result. What can I do to convert the numeric (0) value? Thanks in advance!

回答1:

It is only when we do the +, it is a problem. This can be avoided if we use sum

sum(numeric(0), 5)
#[1] 5
sum(numeric(0), 5, 10)
#[1] 15

Or if we need to use +, an easy option is to concatenate with 0, select the first element. If the element is numeric(0), that gets replaced by 0, for other cases, the first element remain intact

c(numeric(0), 0)[1]
#[1] 0

Using a small example

lst1 <- list(1, 3, numeric(0),  4, numeric(0))
out <- 0
for(i in seq_along(lst1)) {
       out <- out + c(lst1[[i]], 0)[1]
  }

out
#[1] 8

回答2:

You can use max/min with 0 to get 0 as output when input is numeric(0).

x <- 1:10
max(x[FALSE], 0)
#[1] 0

min(x[FALSE], 0)
#[1] 0

来源：https://stackoverflow.com/questions/64236145/addition-involving-numeric0-values