Mercurial > hg > svcore
view base/LogRange.cpp @ 478:1405f4a2caf3
* Add use-log-scale estimator. Not quite right yet; the model doesn't
actually have any data in it yet at the point where we want to make
this decision
* Update changelog
author | Chris Cannam |
---|---|
date | Tue, 11 Nov 2008 13:54:47 +0000 |
parents | 9525c9d7e54d |
children | bdc9bb371a9f |
line wrap: on
line source
/* -*- 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 <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; // std::cerr << "LogRange::mapRange: min = " << min << ", max = " << max << std::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); // std::cerr << "LogRange::mapRange: positive: min = " << min << ", max = " << max << std::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); // std::cerr << "LogRange::mapRange: negative: min = " << min << ", max = " << max << std::endl; } else { // min < 0 and max > 0 max = log10f(std::max(max, -min)); min = std::min(logthresh, max); // std::cerr << "LogRange::mapRange: spanning: min = " << min << ", max = " << max << std::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); std::cerr << "LogRange::useLogScale: sd0 = " << sd0 << ", sd1 = " << sd1 << std::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; }