tweak +ex

man/binomQ.Rd

@@ -16,7 +16,9 @@ dbinomQ(x, size, prob, log = FALSE)
     passed to \code{\link{chooseZ}()}.}
   \item{prob}{the probability; should be big rational
     (\code{"\link{bigq}"}); if not it is coerced with a warning.}
-  \item{log}{logical; must be \code{FALSE} on purpose.}
+  \item{log}{logical; must be \code{FALSE} on purpose.  Use
+    \code{log(Rmpfr::\link[Rmpfr]{mpfr}(dbinomQ(..), precB))} for the
+    logarithm of such big rational numbers.}
 }
 \value{a big rational (\code{"\link{bigq}"}) of the \code{\link{length}} of
   (recycled) \code{x+size+prob}.
@@ -32,10 +34,14 @@ dbinomQ(0:8,8, as.bigq(1,2))
 ph16. <- dbinomQ(0:16, size=16, prob = 1/2)  # innocous warning
 ph16  <- dbinomQ(0:16, size=16, prob = as.bigq(1,2))
 ph16.75 <- dbinomQ(0:16, size=16, prob = as.bigq(3,4))
+ph8.75  <- dbinomQ(0:8, 8, as.bigq(3,4))
 stopifnot(exprs = {
+   dbinomQ(0:8,8, as.bigq(1,2)) * 2^8 == choose(8, 0:8)
+   identical(ph8.75, chooseZ(8,0:8) * 3^(0:8) / 4^8)
+   all.equal(ph8.75, choose (8,0:8) * 3^(0:8) / 4^8, tol=1e-15) # see exactly equal
    identical(ph16, ph16.)
    identical(ph16,
-         dbinomQ(0:16, size=16, prob = as.bigz(1)/2))
+            dbinomQ(0:16, size=16, prob = as.bigz(1)/2))
    all.equal(dbinom(0:16, 16, prob=1/2), asNumeric(ph16),    tol=1e-15)
    all.equal(dbinom(0:16, 16, prob=3/4), asNumeric(ph16.75), tol=1e-15)
 })