static
int
akima_eval_integ (const void * vstate,
const double x_array[], const double y_array[], size_t size,
gsl_interp_accel * acc,
double a, double b,
double * result)
{
const akima_state_t *state = (const akima_state_t *) vstate;
size_t i, index_a, index_b;
if (acc != 0)
{
index_a = gsl_interp_accel_find (acc, x_array, size, a);
index_b = gsl_interp_accel_find (acc, x_array, size, b);
}
else
{
index_a = gsl_interp_bsearch (x_array, a, 0, size - 1);
index_b = gsl_interp_bsearch (x_array, b, 0, size - 1);
}
*result = 0.0;
/* interior intervals */
for(i=index_a; i<=index_b; i++) {
const double x_hi = x_array[i + 1];
const double x_lo = x_array[i];
const double y_lo = y_array[i];
const double dx = x_hi - x_lo;
if(dx != 0.0) {
if (i == index_a || i == index_b)
{
double x1 = (i == index_a) ? a : x_lo;
double x2 = (i == index_b) ? b : x_hi;
*result += integ_eval (y_lo, state->b[i], state->c[i], state->d[i],
x_lo, x1, x2);
}
else
{
*result += dx * (y_lo
+ dx*(0.5*state->b[i]
+ dx*(state->c[i]/3.0
+ 0.25*state->d[i]*dx)));
}
}
else {
*result = 0.0;
return GSL_FAILURE;
}
}
return GSL_SUCCESS;
}
static
int
cspline_eval_integ (const void * vstate,
const double x_array[], const double y_array[], size_t size,
gsl_interp_accel * acc,
double a, double b,
double * result)
{
const cspline_state_t *state = (const cspline_state_t *) vstate;
size_t i, index_a, index_b;
if (acc != 0)
{
index_a = gsl_interp_accel_find (acc, x_array, size, a);
index_b = gsl_interp_accel_find (acc, x_array, size, b);
}
else
{
index_a = gsl_interp_bsearch (x_array, a, 0, size - 1);
index_b = gsl_interp_bsearch (x_array, b, 0, size - 1);
}
*result = 0.0;
/* interior intervals */
for(i=index_a; i<=index_b; i++) {
const double x_hi = x_array[i + 1];
const double x_lo = x_array[i];
const double y_lo = y_array[i];
const double y_hi = y_array[i + 1];
const double dx = x_hi - x_lo;
const double dy = y_hi - y_lo;
if(dx != 0.0) {
double b_i, c_i, d_i;
coeff_calc(state->c, dy, dx, i, &b_i, &c_i, &d_i);
if (i == index_a || i == index_b)
{
double x1 = (i == index_a) ? a : x_lo;
double x2 = (i == index_b) ? b : x_hi;
*result += integ_eval(y_lo, b_i, c_i, d_i, x_lo, x1, x2);
}
else
{
*result += dx * (y_lo + dx*(0.5*b_i + dx*(c_i/3.0 + 0.25*d_i*dx)));
}
}
else {
*result = 0.0;
return GSL_EINVAL;
}
}
return GSL_SUCCESS;
}