Nothing
library(coop)
set.seed(1234)
n <- 21
x = matrix(rnorm(n), 3)
x[sample(n, size=6)] = NA
t1 <- cov(x, use="pair")
t2 <- covar(x, use="pair")
stopifnot(all.equal(t1, t2))
t1 <- cor(x, use="pair")
t2 <- pcor(x, use="pair")
stopifnot(all.equal(t1, t2))
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