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#include <math.h>
#include <stdio.h>
#include "fudgit.h"
/* An example of a user-defined routine inversing the order of an even
* vector. Typical call would be:
* myproc(A_VEC, data)
* from C-calculator mode.
*/
void myproc(X, dn)
VEC X;
expr dn;
{
int i, half_n;
int n = (int)*dn;
double tmp;
if (n%2 == 1) /* report error if odd number (Why not?)*/
fprintf(stderr,"%s: Called with an odd number %d.", "myproc", n);
/* You have full use of stdio library too!!! */
fprintf(stderr, "BTW, Did you know that %lf is the sqrt(pi)?\n",
sqrt(M_PI));
half_n = n >>1; /* half of n */
for (i=0;i<half_n;i++) { /* Standard C: indices go from 0 to data-1 */
tmp = X[i];
X[i] = X[n-i];
X[n-i] = tmp;
}
}
/*
* Another example involving a function. The following calculates the
* non-normalized correlation between vectors A and B as defined by
* corr(A, B) = <A*B> - <A> * <B>
*
*/
double myfunc(A, B, dn)
VEC A, B;
expr dn;
{
int i, n = (int)*dn;
double sumA, sumB, sumAB;
sumA = sumB = sumAB = 0.0;
for (i=0;i<n; i++) {
sumA += A[i];
sumB += B[i];
sumAB += A[i] * B[i];
}
/* leave it simple */
sumA /= *dn;
sumB /= *dn;
sumAB /= *dn;
return (sumAB - sumA*sumB);
}
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