31 lines
1 KiB
Ruby
31 lines
1 KiB
Ruby
# Adapted from https://github.com/thirtysixthspan/descriptive_statistics
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# Copyright (c) 2010-2014 Derrick Parkhurst (derrick.parkhurst@gmail.com)
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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class Array
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def percentile(p)
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values = self.sort
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if values.empty?
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return []
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elsif values.size == 1
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return values.first
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elsif p == 100
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return values.last
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end
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rank = p / 100.0 * (values.size - 1)
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lower, upper = values[rank.floor, 2]
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lower + (upper - lower) * (rank - rank.floor)
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end
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end
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