48 lines
1.2 KiB
Elm
48 lines
1.2 KiB
Elm
-- miscellaneous functions extracted from Main so
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-- we can more easily test them
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module Lib exposing(looseLabels)
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maybe default val =
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case val of
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Just v -> v
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Nothing -> default
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-- https://github.com/cenfun/nice-ticks/blob/master/docs/Nice-Numbers-for-Graph-Labels.pdf
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log10 x = logBase 10 x
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expt b x = b^(toFloat x)
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niceNumber x round =
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let exp = floor (log10 x)
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f = x / (expt 10.0 exp)
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nfRound = if f < 1.5
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then 1
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else if f < 3
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then 2
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else if f < 7
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then 5
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else 10
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nf = if f <= 1
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then 1
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else if f <= 2
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then 2
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else if f <= 5
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then 5
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else 10
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in
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if round
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then
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nfRound * expt 10 exp
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else
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nf * expt 10 exp
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looseLabels ticks min max =
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let
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range = niceNumber (max-min) False
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d = niceNumber (range/(ticks - 1)) True
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graphmin = toFloat (floor (min/d)) * d
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graphmax = toFloat (ceiling (max/d)) * d
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in (graphmin, graphmax, d)
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