view base/LogRange.cpp @ 1247:8f076d02569a piper

Make SVDEBUG always write to a log file -- formerly this was disabled in NDEBUG builds. I think there's little use to that, it just means that we keep adding more cerr debug output because we aren't getting the log we need. And SVDEBUG logging is not usually used in tight loops, I don't think the performance overhead is too serious.

Also update the About box.

/* -*- 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(double &min, double &max, double logthresh)
{
    if (min > max) std::swap(min, max);
    if (max == min) max = min + 1;

//    cerr << "LogRange::mapRange: min = " << min << ", max = " << max << endl;
    
    if (min >= 0.f) {

        max = log10(max); // we know max != 0

        if (min == 0.f) min = std::min(logthresh, max);
        else min = log10(min);

//        cerr << "LogRange::mapRange: positive: min = " << min << ", max = " << max << endl;

    } else if (max <= 0.f) {
        
        min = log10(-min); // we know min != 0
        
        if (max == 0.f) max = std::min(logthresh, min);
        else max = log10(-max);
        
        std::swap(min, max);
        
//        cerr << "LogRange::mapRange: negative: min = " << min << ", max = " << max << endl;

    } else {
        
        // min < 0 and max > 0
        
        max = log10(std::max(max, -min));
        min = std::min(logthresh, max);

//        cerr << "LogRange::mapRange: spanning: min = " << min << ", max = " << max << endl;
    }

    if (min == max) min = max - 1;
}        

double
LogRange::map(double value, double thresh)
{
    if (value == 0.f) return thresh;
    return log10(fabs(value));
}

double
LogRange::unmap(double value)
{
    return pow(10.0, value);
}

static double
sd(const std::vector<double> &values, int start, int n)
{
    double sum = 0.f, mean = 0.f, variance = 0.f;
    for (int i = 0; i < n; ++i) {
        sum += values[start + i];
    }
    mean = sum / n;
    for (int i = 0; i < n; ++i) {
        double diff = values[start + i] - mean;
        variance += diff * diff;
    }
    variance = variance / n;
    return sqrt(variance);
}

bool
LogRange::useLogScale(std::vector<double> 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.

    int n = int(values.size());
    if (n < 4) return false;
    std::sort(values.begin(), values.end());
    int mi = n / 2;

    double sd0 = sd(values, 0, mi);
    double sd1 = sd(values, mi, n - 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.) return true;
    else return false;
}