//
// ti2favg -- Convert time interval to smoothed frequency average.
//
// - Frequency is usually calculated from phase using non-overlapping
//   averaging intervals. The longer the averaging interval the fewer
//   the number of frequency points and the more sparse the plot.
//
// - With this tool we use overlapping averaging intervals which makes
//   frequency plots as dense as the corresponding raw phase plots.
//
// - Input is phase (time interval), output is smoothed frequency.
//
// 20-Oct-2008 /tvb
//

#include <stdio.h>
#include <stdlib.h>

#define MAX_HIST (1 << 17)
double data[MAX_HIST];
#define WRAP(n) ( (n) % MAX_HIST )

int main (int argc, char *argv[])
{
    char line[1000];
    unsigned long count, window, slide;
    double scale, favg;

    if (argc == 1) {
        fprintf(stderr, "%s [window] [slide] [scale]\n", argv[0]);
        exit(1);
    }

    // Get averaging window.

    window = (argc > 1) ? (long)atof(argv[1]) : 1;
    if (window < 1 || window >= MAX_HIST) {
        fprintf(stderr, "bad window %ld\n", window);
        exit(1);
    }
    fprintf(stderr, "window: %ld\n", window);

    // Get sliding window increment.
    //   NOTE: slide = 1 for fully overlapped, running average
    //         slide = window for back-to-back, conventional average

    slide = (argc > 2) ? atof(argv[2]) : window;
    if (slide < 1 || slide > window) {
        fprintf(stderr, "bad slide %lg\n", slide);
        exit(1);
    }
    fprintf(stderr, "slide:  %ld\n", slide);

    // Get (optional) data scaling factor.

    scale = (argc > 3) ? atof(argv[3]) : 1.0;
    if (scale == 0.0) {
        fprintf(stderr, "bad scale %lg\n", scale);
        exit(1);
    }
    fprintf(stderr, "scale:  %.3lg\n", scale);

    for (count = 0; NULL != fgets(line, sizeof line, stdin); count += 1) {
        data[WRAP(count)] = atof(line) * scale;
        if (count >= window && (count % slide) == 0) {
            favg = (data[WRAP(count)] - data[WRAP(count - window)]) / window;
            printf("%ld %.16le\n", count, favg);
        }
    }
    fprintf(stderr, "count:  %ld\n", count);
}