cd940f7fd3
Add a new helper function Histogram::interBinMean() that essentially replaces the existing Histogram::interQuantileMean() logic but working on bins instead. Rework the interQuantileMean() to call into interBinMean() with the appropriate convertion from quatiles to bins. Signed-off-by: Naushir Patuck <naush@raspberrypi.com> Reviewed-by: David Plowman <david.plowman@raspberrypi.com> Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
71 lines
1.8 KiB
C++
71 lines
1.8 KiB
C++
/* SPDX-License-Identifier: BSD-2-Clause */
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/*
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* Copyright (C) 2019, Raspberry Pi Ltd
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*
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* histogram.cpp - histogram calculations
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*/
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#include <math.h>
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#include <stdio.h>
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#include "histogram.h"
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using namespace RPiController;
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uint64_t Histogram::cumulativeFreq(double bin) const
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{
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if (bin <= 0)
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return 0;
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else if (bin >= bins())
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return total();
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int b = (int)bin;
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return cumulative_[b] +
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(bin - b) * (cumulative_[b + 1] - cumulative_[b]);
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}
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double Histogram::quantile(double q, int first, int last) const
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{
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if (first == -1)
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first = 0;
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if (last == -1)
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last = cumulative_.size() - 2;
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assert(first <= last);
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uint64_t items = q * total();
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while (first < last) /* binary search to find the right bin */
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{
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int middle = (first + last) / 2;
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if (cumulative_[middle + 1] > items)
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last = middle; /* between first and middle */
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else
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first = middle + 1; /* after middle */
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}
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assert(items >= cumulative_[first] && items <= cumulative_[last + 1]);
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double frac = cumulative_[first + 1] == cumulative_[first] ? 0
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: (double)(items - cumulative_[first]) /
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(cumulative_[first + 1] - cumulative_[first]);
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return first + frac;
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}
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double Histogram::interBinMean(double binLo, double binHi) const
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{
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assert(binHi > binLo);
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double sumBinFreq = 0, cumulFreq = 0;
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for (double binNext = floor(binLo) + 1.0; binNext <= ceil(binHi);
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binLo = binNext, binNext += 1.0) {
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int bin = floor(binLo);
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double freq = (cumulative_[bin + 1] - cumulative_[bin]) *
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(std::min(binNext, binHi) - binLo);
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sumBinFreq += bin * freq;
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cumulFreq += freq;
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}
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/* add 0.5 to give an average for bin mid-points */
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return sumBinFreq / cumulFreq + 0.5;
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}
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double Histogram::interQuantileMean(double qLo, double qHi) const
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{
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assert(qHi > qLo);
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double pLo = quantile(qLo);
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double pHi = quantile(qHi, (int)pLo);
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return interBinMean(pLo, pHi);
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}
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