Cumulative standard deviation: Difference between revisions
→{{header|AppleScript}}: Added a map-accumulation variant.
(→{{header|Haskell}}: Switched foldl version to a more natural expression in terms of mapAccumL) |
(→{{header|AppleScript}}: Added a map-accumulation variant.) |
||
Line 518:
<lang AppleScrip>{0.0, 1.0, 0.942809041582, 0.866025403784,
0.979795897113, 1.0, 1.399708424448, 2.0}</lang>
Or as a map-accumulation:
<lang applescript>-------------- CUMULATIVE STANDARD DEVIATION -------------
-- cumulativeStdDevns :: [Float] -> [Float]
on cumulativeStdDevns(xs)
script go
on |λ|(sq, x, i)
set {s, q} to sq
set _s to x + s
set _q to q + (x ^ 2)
{{_s, _q}, ((_q / i) - ((_s / i) ^ 2)) ^ 0.5}
end |λ|
end script
item 2 of mapAccumL(go, {0, 0}, xs)
end cumulativeStdDevns
--------------------------- TEST -------------------------
on run
cumulativeStdDevns({2, 4, 4, 4, 5, 5, 7, 9})
end run
------------------------- GENERIC ------------------------
-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
tell mReturn(f)
set v to startValue
set lng to length of xs
repeat with i from 1 to lng
set v to |λ|(v, item i of xs, i, xs)
end repeat
return v
end tell
end foldl
-- mapAccumL :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y])
on mapAccumL(f, acc, xs)
-- 'The mapAccumL function behaves like a combination of map and foldl;
-- it applies a function to each element of a list, passing an
-- accumulating parameter from |Left| to |Right|, and returning a final
-- value of this accumulator together with the new list.' (see Hoogle)
script
on |λ|(a, x, i)
tell mReturn(f) to set pair to |λ|(item 1 of a, x, i)
{item 1 of pair, (item 2 of a) & {item 2 of pair}}
end |λ|
end script
foldl(result, {acc, []}, xs)
end mapAccumL
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
-- 2nd class handler function lifted into 1st class script wrapper.
if script is class of f then
f
else
script
property |λ| : f
end script
end if
end mReturn</lang>
{{Out}}
<pre>{0.0, 1.0, 0.942809041582, 0.866025403784, 0.979795897113, 1.0, 1.399708424448, 2.0}</pre>
=={{header|AutoHotkey}}==
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