41 lines
1.2 KiB
Elixir
41 lines
1.2 KiB
Elixir
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defmodule Growth.Calc.Age do
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@moduledoc """
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Calculate the age in months.
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"""
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# NOTE: (jpd): based on [WHO instructions][0]
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# [0]: https://cdn.who.int/media/docs/default-source/child-growth/child-growth-standards/indicators/instructions-en.pdf
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@day_in_month 30.4375
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@day_in_week 7.0
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@doc """
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Calculate the age with the precision of day, or week, or month. For age in weeks or months, considers completed ones, removing decimal value.
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If only date of birth is available, assumes that measurement date is today.
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"""
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@spec calculate(:day | :week | :month, Date.t(), Date.t()) :: pos_integer()
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def calculate(precision, date_of_birth) do
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calculate(precision, date_of_birth, Date.utc_today())
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end
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def calculate(:month, date_of_birth, date_of_measurement) do
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:day
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|> calculate(date_of_birth, date_of_measurement)
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|> Kernel./(@day_in_month)
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|> floor()
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end
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def calculate(:week, date_of_birth, date_of_measurement) do
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:day
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|> calculate(date_of_birth, date_of_measurement)
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|> Kernel./(@day_in_week)
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|> floor()
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end
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def calculate(:day, date_of_birth, date_of_measurement) do
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Date.diff(date_of_measurement, date_of_birth)
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end
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end
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