NAG Library Manual, Mark 27.2
/* nag_univar_estim_weibull (g07bec) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

#include <nag.h>
#include <stdio.h>

int main(void) {

/* Scalars */
double beta, corr, dev, gamma, sebeta, segam, tol;
Integer exit_status, i, maxit, n, nit;
NagError fail;

/* Arrays */
double *x = 0;
Integer *ic = 0;

INIT_FAIL(fail);

exit_status = 0;
printf("nag_univar_estim_weibull (g07bec) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);

/* Allocate memory */
if (!(x = NAG_ALLOC(n, double)) || !(ic = NAG_ALLOC(n, Integer))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

for (i = 1; i <= n; ++i)
scanf("%lf", &x[i - 1]);
scanf("%*[^\n] ");

/* If data were censored then ic would also be read in.
*  Leave nag_univar_estim_weibull (g07bec) to calculate initial values
*/
gamma = 0.0;
/* Use default values for tol and maxit */
tol = 0.0;
maxit = 0;
/* nag_univar_estim_weibull (g07bec).
* Computes maximum likelihood estimates for parameters of
* the Weibull distribution
*/
nag_univar_estim_weibull(Nag_NoCensored, n, x, ic, &beta, &gamma, tol, maxit,
&sebeta, &segam, &corr, &dev, &nit, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_univar_estim_weibull (g07bec).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

printf("\n");
printf("Beta  = %10.4f Standard error = %10.4f\n", beta, sebeta);
printf("Gamma = %10.4f Standard error = %10.4f\n", gamma, segam);
END:
NAG_FREE(x);
NAG_FREE(ic);
return exit_status;
}