Cumulative standard deviation: Difference between revisions
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m (→{{header|Haskell}}: Tidying) |
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Or, as a map-accumulation over an indexed list |
Or, perhaps more simply, as a map-accumulation over an indexed list: |
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<lang Haskell>import Data.List (mapAccumL) |
<lang Haskell>import Data.List (mapAccumL) |
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-------------- CUMULATIVE STANDARD DEVIATION ------------- |
-------------- CUMULATIVE STANDARD DEVIATION ------------- |
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cumulativeStdDevns :: [Float] -> [Float] |
cumulativeStdDevns :: [Float] -> [Float] |
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cumulativeStdDevns xs = snd $ mapAccumL go (0, 0) $ zip [1 ..] xs |
cumulativeStdDevns xs = snd $ mapAccumL go (0, 0) $ zip [1.0 ..] xs |
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where |
where |
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go (s, q) (i, x) = |
go (s, q) (i, x) = |
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let _s = s + x |
let _s = s + x |
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_q = q + (x ^ 2) |
_q = q + (x ^ 2) |
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in ((_s, _q), sqrt ((_q / i) - ((_s / i) ^ 2))) |
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in ((_s, _q), sqrt ((_q / _i) - ((_s / _i) ^ 2))) |
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--------------------------- TEST ------------------------- |
--------------------------- TEST ------------------------- |
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main :: IO () |
main :: IO () |
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