diff options
Diffstat (limited to 'bin')
| -rw-r--r-- | bin/cluster.hs | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/bin/cluster.hs b/bin/cluster.hs index 42e25dc..67b6e02 100644 --- a/bin/cluster.hs +++ b/bin/cluster.hs @@ -25,11 +25,13 @@ logFromInt = logFrom . fromIntegral logFrom = Exp . log binom :: Int -> Int -> Double -> Log Double -binom 0 _ _ = 1 -binom n 0 p = logFrom (1 - p) ** logFromInt n -binom n@(logFromInt -> n') k@(logFromInt -> k') p@(logFrom -> p') = choose * p' ** k' * logFrom (1 - p) ** (n' - k') +binom n@(logFromInt -> n') k@(logFromInt -> k') p + | n == 0 = 1 + | k == 0 = logFrom (1 - p) ** logFromInt n + | k == n = logFrom p ** logFromInt n + | otherwise = n `choose` k * logFrom p ** k' * logFrom (1 - p) ** (n' - k') where - choose = product [(n' + 1 - logFromInt i) / logFromInt i | i <- [1 .. k]] + choose (fromIntegral -> n) (fromIntegral -> k) = stirling n / stirling k / stirling (n - k) -- (infinite) binary trees data Tree a = Tree a (Tree a) (Tree a) |