module Statistics.Distribution.Uniform (
UniformDistribution
, uniformDistr
) where
import Data.Typeable (Typeable)
import qualified Statistics.Distribution as D
data UniformDistribution = UniformDistribution !Double !Double
deriving (Eq,Show,Read,Typeable)
uniformDistr :: Double -> Double -> UniformDistribution
uniformDistr a b
| b < a = uniformDistr b a
| a < b = UniformDistribution a b
| otherwise = error "Statistics.Distribution.Uniform.uniform: wrong parameters"
instance D.Distribution UniformDistribution where
cumulative (UniformDistribution a b) x
| x < a = 0
| x > b = 1
| otherwise = (x a) / (b a)
instance D.ContDistr UniformDistribution where
density (UniformDistribution a b) x
| x < a = 0
| x > b = 0
| otherwise = 1 / (b a)
quantile (UniformDistribution a b) p
| p >= 0 && p <= 1 = a + (b a) * p
| otherwise =
error $ "Statistics.Distribution.Uniform.quantile: p must be in [0,1] range. Got: "++show p
instance D.Mean UniformDistribution where
mean (UniformDistribution a b) = 0.5 * (a + b)
instance D.Variance UniformDistribution where
stdDev (UniformDistribution a b) = 0.2886751345948129 * (b a)
variance (UniformDistribution a b) = d * d / 12 where d = b a
instance D.MaybeMean UniformDistribution where
maybeMean = Just . D.mean
instance D.MaybeVariance UniformDistribution where
maybeStdDev = Just . D.stdDev