/*
linsamp.c Joe Mietus Dec 19 2001
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linsamp: Resample stdin by linear interpolation, output evenly sampled data
Copyright (C) 2002 Joe Mietus
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.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA.
You may contact the author by e-mail (joe at physionet dot org) or postal mail
(MIT Room E25-505A, Cambridge, MA 02139 USA). For updates to this software,
please visit PhysioNet (http://www.physionet.org/).
_______________________________________________________________________________
Resample stdin by linear interpolation, output evenly sampled data
Usage : linsamp dt
dt : sampling interval
*/
#include <stdio.h>
#include <stdlib.h>
main(argc, argv)
int argc;
char *argv[];
{
int i;
double dx, x0, x[2], y[2];
double intrpolt();
if (argc != 2 ) {
usage(argv[0]);
exit(1);
}
if ((dx = atof(argv[1])) <= 0) {
fprintf(stderr, "%s : dt must be greater than 0\n", argv[0]);
exit(1);
}
for (i=0; i<2; i++)
if (scanf("%lf %lf", &x[i], &y[i]) < 2)
exit(1);
printf("%g %g\n", x[0], y[0]);
x0 = x[0] + dx;
for ( ; ; ) {
while (x0 > x[1]) {
x[0] = x[1];
y[0] = y[1];
if (scanf("%lf %lf", &x[1], &y[1]) < 2 )
exit(0); /* Normal exit from program */
}
printf("%g %g\n", x0, intrpolt(x0, x, y));
x0 += dx;
}
}
double intrpolt(x0, x, y)
double x0, *x, *y;
{
double a, b;
b = (y[1] - y[0]) / (x[1] - x[0]);
a = y[0] - b*x[0];
return(b*x0 + a);
}
usage(prog)
char *prog;
{
fprintf(stderr, "Usage : %s dt\n\n", prog);
fprintf(stderr, " Resample stdin by linear interpolation\n");
fprintf(stderr, " Output evenly sampled data\n\n");
fprintf(stderr, " dt : sampling interval\n");
}