ftest is a package demonstrating how to call an R function from Fortran

A complete example is provided.

Examples

## Suppose we wish to call `r_fun` from Fortran

r_fun <- function(y, z, w) {
   w  <- w / sum(w)
   sum((y - z)^2 * w / sum(w))
}

y = 1:10; z = 11:20; w = rep(1, 10);
r_fun(y = y, z = z, w = w) # 100!
#> [1] 100

## Write the r_from_f function as below.

r_from_f  <- function(r_fun, y, z, w) {
   ## save the R function to call in C ; fcallr knows to look for it there.
   save_rfunc(r_fun)
   u <- .Fortran("fcallr",
                 length(y),
                 as.double(y),
                 as.double(z),
                 as.double(w),
                 result = as.double(0), PACKAGE = "ftest")
   u$result
}

stopifnot(r_from_f(r_fun, y, z, w) == r_fun(y, z, w))

r_from_f(r_fun, y, z, w)
#> [1] 100