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82 lines
1.9 KiB
82 lines
1.9 KiB
4 months ago
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/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <stdlib.h>
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#include <cpustats/CentralTendencyStatistics.h>
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void CentralTendencyStatistics::sample(double x)
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{
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// update min and max
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if (x < mMinimum)
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mMinimum = x;
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if (x > mMaximum)
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mMaximum = x;
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// Knuth
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if (mN == 0) {
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mMean = 0;
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}
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++mN;
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double delta = x - mMean;
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mMean += delta / mN;
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mM2 += delta * (x - mMean);
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}
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void CentralTendencyStatistics::reset()
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{
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mMean = NAN;
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mMedian = NAN;
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mMinimum = INFINITY;
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mMaximum = -INFINITY;
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mN = 0;
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mM2 = 0;
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mVariance = NAN;
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mVarianceKnownForN = 0;
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mStddev = NAN;
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mStddevKnownForN = 0;
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}
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double CentralTendencyStatistics::variance() const
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{
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double variance;
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if (mVarianceKnownForN != mN) {
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if (mN > 1) {
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// double variance_n = M2/n;
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variance = mM2 / (mN - 1);
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} else {
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variance = NAN;
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}
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mVariance = variance;
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mVarianceKnownForN = mN;
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} else {
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variance = mVariance;
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}
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return variance;
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}
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double CentralTendencyStatistics::stddev() const
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{
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double stddev;
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if (mStddevKnownForN != mN) {
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stddev = sqrt(variance());
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mStddev = stddev;
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mStddevKnownForN = mN;
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} else {
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stddev = mStddev;
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}
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return stddev;
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}
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