e02gace.c

/* nag_fit_glin_l1sol (e02gac) Example Program.
 *
 * Copyright 2025 Numerical Algorithms Group.
 *
 * Mark 31.1, 2025.
 */
#include<math.h>
#include<nag.h>
#include<stdio.h>
intmain(void){
/* Scalars */
doubleresid,t,tol;
Integerexit_status,i,iter,m,rank,n,nplus2,pda;
NagErrorfail;
Nag_OrderTypeorder;
/* Arrays */
double*a=0,*b=0,*x=0;
#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
order=Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
order=Nag_RowMajor;
#endif
INIT_FAIL(fail);
exit_status=0;
printf("nag_fit_glin_l1sol (e02gac) Example Program Results\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
n=3;
nplus2=n+2;
scanf("%"NAG_IFMT"%*[^\n] ",&m);
if(m>0){
/* Allocate memory */
if(!(a=NAG_ALLOC((m+2)*nplus2,double))||
!(b=NAG_ALLOC(m,double))||!(x=NAG_ALLOC(nplus2,double))){
printf("Allocation failure\n");
exit_status=-1;
gotoEND;
}
if(order==Nag_ColMajor)
pda=m+2;
else
pda=nplus2;
for(i=1;i<=m;++i){
scanf("%lf%lf%*[^\n] ",&t,&b[i-1]);
A(i,1)=exp(t);
A(i,2)=exp(-t);
A(i,3)=1.0;
}
tol=0.0;
/* nag_fit_glin_l1sol (e02gac).
 * L_1-approximation by general linear function
 */
nag_fit_glin_l1sol(order,m,a,b,nplus2,tol,x,&resid,&rank,&iter,
&fail);
if(fail.code==NE_INT||fail.code==NE_INT_2||
fail.code==NE_TOO_MANY_ITER||fail.code==NE_NO_LICENCE){
printf("Error from nag_fit_glin_l1sol (e02gac).\n%s\n",fail.message);
exit_status=1;
gotoEND;
}else{
printf("\n");
printf("resid = %11.2e Rank = %5"NAG_IFMT" Iterations ="
" %5"NAG_IFMT"\n",
resid,rank,iter);
printf("\n");
printf("Solution\n");
for(i=1;i<=n;++i)
printf("%10.4f",x[i-1]);
printf("\n");
}
}
END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(x);
returnexit_status;
}