Mderiv.c

/* First derivative with a maximally linear FIR differentiator. 

May 2012 program of the month:
http://ahay.org/blog/2012/05/01/program-of-the-month-sfderiv/
*/
/*
  Copyright (C) 2004 University of Texas at Austin

  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
*/

#include <rsf.h>

int main (int argc, char* argv[])
{
    bool scale;
    int n1,n2, i1,i2, n;
    float d1, *dat, *der;
    sf_file in=NULL, out=NULL;

    sf_init (argc,argv);
    in = sf_input("in");
    out = sf_output("out");

    if (SF_FLOAT != sf_gettype(in)) sf_error("Need float input");
    if (!sf_histint(in,"n1",&n1)) sf_error("No n1= in input");
    n2 = sf_leftsize(in,1);

    dat = sf_floatalloc(n1);
    der = sf_floatalloc(n1);

    if (!sf_getint("order",&n)) n=6;
    /* filter order */

    if (!sf_getbool("scale",&scale) || 
	!sf_histfloat(in,"d1",&d1)) scale=false;
    /*(scale=n if scale by 1/dx )*/

    sf_deriv_init(n1, n, 0.);

    for (i2=0; i2 < n2; i2++) {
	sf_floatread(dat,n1,in);
	sf_deriv(dat,der);

	if (scale) {
	    for (i1=0; i1 < n1; i1++) {
		der[i1] /= d1;
	    }
	}

	sf_floatwrite(der,n1,out);
    }


    exit(0);
}