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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
/*
Sonic Visualiser
An audio file viewer and annotation editor.
Centre for Digital Music, Queen Mary, University of London.
This file copyright 2006 Chris Cannam.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version. See the file
COPYING included with this distribution for more information.
*/
#include "LogRange.h"
#include "system/System.h"
#include <algorithm>
#include <iostream>
#include <cmath>
void
LogRange::mapRange(float &min, float &max, float logthresh)
{
if (min > max) std::swap(min, max);
if (max == min) max = min + 1;
// SVDEBUG << "LogRange::mapRange: min = " << min << ", max = " << max << endl;
if (min >= 0.f) {
max = log10f(max); // we know max != 0
if (min == 0.f) min = std::min(logthresh, max);
else min = log10f(min);
// SVDEBUG << "LogRange::mapRange: positive: min = " << min << ", max = " << max << endl;
} else if (max <= 0.f) {
min = log10f(-min); // we know min != 0
if (max == 0.f) max = std::min(logthresh, min);
else max = log10f(-max);
std::swap(min, max);
// SVDEBUG << "LogRange::mapRange: negative: min = " << min << ", max = " << max << endl;
} else {
// min < 0 and max > 0
max = log10f(std::max(max, -min));
min = std::min(logthresh, max);
// SVDEBUG << "LogRange::mapRange: spanning: min = " << min << ", max = " << max << endl;
}
if (min == max) min = max - 1;
}
float
LogRange::map(float value, float thresh)
{
if (value == 0.f) return thresh;
return log10f(fabsf(value));
}
float
LogRange::unmap(float value)
{
return powf(10.0, value);
}
static float
sd(const std::vector<float> &values, size_t start, size_t n)
{
float sum = 0.f, mean = 0.f, variance = 0.f;
for (size_t i = 0; i < n; ++i) {
sum += values[start + i];
}
mean = sum / n;
for (size_t i = 0; i < n; ++i) {
float diff = values[start + i] - mean;
variance += diff * diff;
}
variance = variance / n;
return sqrtf(variance);
}
bool
LogRange::useLogScale(std::vector<float> values)
{
// Principle: Partition the data into two sets around the median;
// calculate the standard deviation of each set; if the two SDs
// are very different, it's likely that a log scale would be good.
if (values.size() < 4) return false;
std::sort(values.begin(), values.end());
size_t mi = values.size() / 2;
float sd0 = sd(values, 0, mi);
float sd1 = sd(values, mi, values.size() - mi);
SVDEBUG << "LogRange::useLogScale: sd0 = "
<< sd0 << ", sd1 = " << sd1 << endl;
if (sd0 == 0 || sd1 == 0) return false;
// I wonder what method of determining "one sd much bigger than
// the other" would be appropriate here...
if (std::max(sd0, sd1) / std::min(sd0, sd1) > 10.f) return true;
else return false;
}
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