//
// Convert frequency to Time interval error.
//
// - Input is a file of frequency readings.
// - User gives nominal frequency.
// - User gives sample period.
// - Output is accumulated time error.
//
// 14-Mar-2009 tvb
//

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

void main (int argc, char *argv[])
{
    double Count, f0, t0, f, t;
    char Format[1000], Line[1000], TimeStamp[1000];

    if (argc < 2) {
        fprintf(stderr, "Usage: %s [f0] [tau] [format]\n", argv[0]);
        exit(0);
    }

    f0 = (argc > 1) ? atof(argv[1]) : 1.0;
    fprintf(stderr, "f0 %lg\n", f0);

    t0 = (argc > 2) ? atof(argv[2]) : 1.0;
    fprintf(stderr, "t0 %lg\n", t0);

    sprintf(Format, "%%%s\n", (argc > 3) ? argv[3] : ".12lg");
    fprintf(stderr, "format %s", Format);

    t = 0.0;
    for (Count = 0; fgets(Line, sizeof(Line), stdin) != NULL; Count += 1) {
        // TimeStamp is optional
        if (2 == sscanf(Line, "%s %lf", TimeStamp, &f)) {
            printf("%s ", TimeStamp);
        } else {
            sscanf(Line, "%lf", &f);
        }
        t += ((f - f0) / f0) * t0;
        printf(Format, t);
    }
}

#if 0

Sample input file:

C:\tvb\cl> field 2 < \tmp\log23475.dat | head -5
60.0065776684
60.0080932691
60.0061470697
60.0023879296
60.0023691993

These are 100 second average 60 Hz mains frequency measurements.

Sampe usage:

C:\tvb\cl> field 2 < \tmp\log23475.dat | fr2ti 60 100 | head -5
0.0109627806666642
0.0244515625000001
0.0346966786666651
0.0386765613333277
0.0426252268333253

or, keeping time stamps:

C:\tvb\cl> fr2ti 60 100 .6le < \tmp\log23475.dat | head -5
f0 60
t0 100
format %.6le
53750.320438 1.096278e-002
53750.321597 2.445156e-002
53750.322756 3.469668e-002
53750.323915 3.867656e-002
53750.325074 4.262523e-002

#endif