module Statistics.Distribution.Geometric
(
GeometricDistribution
, geometric
, gdSuccess
) where
import Control.Exception (assert)
import Data.Typeable (Typeable)
import qualified Statistics.Distribution as D
newtype GeometricDistribution = GD {
gdSuccess :: Double
} deriving (Eq, Read, Show, Typeable)
instance D.Distribution GeometricDistribution where
cumulative = cumulative
instance D.DiscreteDistr GeometricDistribution where
probability = probability
instance D.Variance GeometricDistribution where
variance (GD s) = (1 s) / (s * s)
instance D.Mean GeometricDistribution where
mean (GD s) = 1 / s
geometric :: Double
-> GeometricDistribution
geometric x = assert (x >= 0 && x <= 1)
GD x
probability :: GeometricDistribution -> Int -> Double
probability (GD s) n | n < 1 = 0
| otherwise = s * (1s) ** (fromIntegral n 1)
cumulative :: GeometricDistribution -> Double -> Double
cumulative (GD s) x | x < 1 = 0
| otherwise = 1 (1s) ^ (floor x :: Int)