"combos" <- function(n,p){
if(length(n) != 1){
n <- n[1]
warning("Using first element as n")
}
if(length(p) != 1){
p <- p[1]
warning("Using first element as p")
}
if(n != as.integer(n)){
warning("Coercing n to integer")
n <- as.integer(n)
}
if(p != as.integer(p)){
warning("Coercing p to integer")
p <- as.integer(p)
}
if(p > n) stop("p is greater than n")
m <- choose(n,p)
z <- .Fortran("combin",
as.integer(n),
as.integer(p),
as.integer(m),
a = integer(p*m),
integer(n),
integer(n),
integer(n),
PACKAGE = "quantreg")
matrix(z$a,p)
}