104 lines
2.6 KiB
Elm
104 lines
2.6 KiB
Elm
module Point exposing(Pos, Point, decoder, downsample, duration, subseq, startTime, centre)
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import Json.Decode as D
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type alias Pos =
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{ lat : Float
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, lon : Float
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, ele : Maybe Float
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}
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type alias Point =
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{ time : Float
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, pos : Pos
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, cadence : Maybe Int
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, power : Maybe Int
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, heartRate : Maybe Int
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}
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posDecoder : D.Decoder Pos
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posDecoder = D.map3 Pos
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(D.field "lat" D.float)
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(D.field "lon" D.float)
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(D.field "ele" (D.maybe D.float))
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decoder : D.Decoder Point
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decoder = D.map5 Point
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(D.field "time" D.float)
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(D.field "pos" posDecoder)
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(D.field "cadence" (D.maybe D.int))
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(D.field "power" (D.maybe D.int))
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(D.field "heartRate" (D.maybe D.int))
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last x xs =
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case xs of
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[] -> x
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(x_::xs_) -> last x_ xs_
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tracef x = Debug.log (String.fromFloat x) x
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-- divide the points into n equal time buckets and return the first
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-- point in each
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downsample n points =
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let
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nextpoint step prev points_ =
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case points_ of
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(next::rest) ->
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if next.time - prev.time > step
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then prev :: (nextpoint step next rest)
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else nextpoint step prev rest
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_ -> [prev]
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in
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case points of
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(first::rest) ->
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let step = (duration points) / (toFloat n)
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in nextpoint step first rest
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[] -> []
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duration points =
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case points of
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(p::ps) -> (last p ps).time - p.time
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_ -> 0
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startTime points =
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case points of
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(p::ps) -> Just p.time
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_ -> Nothing
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type Bound = Bound Pos Pos | NoBound
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extendBound : Pos -> Bound -> Bound
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extendBound pos b =
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let {lat, lon} = pos
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in case b of
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(Bound p1 p2) ->
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Bound
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(Pos (min lat p1.lat) (min lon p1.lon) Nothing)
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(Pos (max lat p2.lat) (max lon p2.lon) Nothing)
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NoBound ->
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Bound pos pos
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bounds points =
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List.foldr extendBound NoBound (List.map .pos points)
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centre points =
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case bounds points of
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Bound min max -> Pos
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((max.lat + min.lat) / 2)
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((max.lon + min.lon) / 2)
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Nothing
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NoBound -> Pos 0 0 Nothing
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subseq points start dur =
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case points of
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[] -> []
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(p::ps) ->
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if p.time < start
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then subseq ps start dur
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else if p.time >= (start + dur)
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then []
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else p::(subseq ps start dur)
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