31 lines
1.0 KiB
Ruby
31 lines
1.0 KiB
Ruby
# frozen_string_literal: true
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#
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# Copyright (C) 2013 - present Instructure, Inc.
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#
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# This file is part of Canvas.
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#
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# Canvas is free software: you can redistribute it and/or modify it under
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# the terms of the GNU Affero General Public License as published by the Free
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# Software Foundation, version 3 of the License.
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#
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# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Affero General Public License along
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# with this program. If not, see <http://www.gnu.org/licenses/>.
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module SimpleStats
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def variance(items, type = :population)
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return 0 if items.size < 2
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divisor = (type == :population) ? items.length : items.length - 1
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mean = items.sum / items.length.to_f
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sum = items.sum { |item| (item - mean)**2 }
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(sum / divisor).to_f
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end
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module_function :variance
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end
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