[R] For loop with multiple iteration indexes

[David Disabato]

Hi R-help,

I am trying to create a for loop with multiple iteration indexes. I don't
want to use two different for loops nested together because I don't need
the full matrix of the two indexes, just the diagonal elements (e.g., i[1]
& j[1] and i[2] & j[2], but not i[1] & j[2]). Is there a way to specify
both i and j in a single for loop? Here is a simplified example of
pseudo-code where x and y are equally sized character vectors with column
names and dat is their dataframe (obviously this code doesn't run in R, but
hopefully you perceive my goal):

r <- list()
n <- 0
for (i in x; j in y) {
   n <- n + 1
   r[[n]] <- cor(x = dat[, i], y = dat[, j])
}
print(r)

I realize there are other solutions to this particular correlation example,
but my actual problem is much more complicated, so I am hoping for a
solution that generalizes across any code within the for loop.

-- 
David J. Disabato, M.A.
Clinical Psychology Doctoral Student
George Mason University
ddisabat using gmu.edu

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