scalar sasfit_peak_GiddingsAmplitude(scalar x, sasfit_param * param)
{
scalar y, bckgr, a_tmp, amplitude, center, width, y0, x0;
gsl_sf_result besselI1;
int status;
SASFIT_ASSERT_PTR( param );
sasfit_get_param(param, 4, &litude, ¢er, &width, &bckgr);
SASFIT_CHECK_COND1((width <= 0), param, "width(%lg) <= 0 ",width);
SASFIT_CHECK_COND1((center <= 0), param, "center(%lg) <= 0 ",center);
gsl_set_error_handler_off();
if (x<0) return bckgr;
a_tmp = amplitude;
param->p[0]=1.0;
x0=x;
x = sasfit_peak_GiddingsMode(param);
param->p[0]=a_tmp;
if (x0==0.0) {
y0 = exp(-center/width)*center/gsl_pow_2(width);
} else {
status = gsl_sf_bessel_I1_e(2*sqrt(center*x)/width,&besselI1);
if (status) {
// SASFIT_CHECK_COND1((status != 0), param, "%s",gsl_strerror(status));
// return 0;
besselI1.val = 0;
}
y0 = 1.0/width * sqrt(center/x) *
besselI1.val*
exp((-x-center)/width);
}
x = x0;
if (x==0.0) {
y = bckgr +
amplitude/y0;
} else {
status = gsl_sf_bessel_I1_e(2*sqrt(center*x)/width,&besselI1);
if (status) {
// SASFIT_CHECK_COND1((status != 0), param, "%s",gsl_strerror(status));
// return 0;
besselI1.val = 0;
}
y = bckgr +
amplitude/y0/width * sqrt(center/x) *
besselI1.val*
exp((-x-center)/width);
}
return y;
}
int gsl_sf_bessel_K1_e(const double x, gsl_sf_result * result)
{
/* CHECK_POINTER(result) */
if(x <= 0.0) {
DOMAIN_ERROR(result);
}
else if(x < 2.0*GSL_DBL_MIN) {
OVERFLOW_ERROR(result);
}
else if(x <= 2.0) {
const double lx = log(x);
int stat_I1;
gsl_sf_result I1;
gsl_sf_result c;
cheb_eval_e(&bk1_cs, 0.5*x*x-1.0, &c);
stat_I1 = gsl_sf_bessel_I1_e(x, &I1);
result->val = (lx-M_LN2)*I1.val + (0.75 + c.val)/x;
result->err = c.err/x + fabs(lx)*I1.err;
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
return stat_I1;
}
else {
gsl_sf_result K1_scaled;
int stat_K1 = gsl_sf_bessel_K1_scaled_e(x, &K1_scaled);
int stat_e = gsl_sf_exp_mult_err_e(-x, 0.0,
K1_scaled.val, K1_scaled.err,
result);
result->err = fabs(result->val) * (GSL_DBL_EPSILON*fabs(x) + K1_scaled.err/K1_scaled.val);
return GSL_ERROR_SELECT_2(stat_e, stat_K1);
}
}
int gsl_sf_bessel_K1_scaled_e(const double x, gsl_sf_result * result)
{
/* CHECK_POINTER(result) */
if(x <= 0.0) {
DOMAIN_ERROR(result);
}
else if(x < 2.0*GSL_DBL_MIN) {
OVERFLOW_ERROR(result);
}
else if(x <= 2.0) {
const double lx = log(x);
const double ex = exp(x);
int stat_I1;
gsl_sf_result I1;
gsl_sf_result c;
cheb_eval_e(&bk1_cs, 0.5*x*x-1.0, &c);
stat_I1 = gsl_sf_bessel_I1_e(x, &I1);
result->val = ex * ((lx-M_LN2)*I1.val + (0.75 + c.val)/x);
result->err = ex * (c.err/x + fabs(lx)*I1.err);
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
return stat_I1;
}
else if(x <= 8.0) {
const double sx = sqrt(x);
gsl_sf_result c;
cheb_eval_e(&ak1_cs, (16.0/x-5.0)/3.0, &c);
result->val = (1.25 + c.val) / sx;
result->err = c.err / sx;
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
return GSL_SUCCESS;
}
else {
const double sx = sqrt(x);
gsl_sf_result c;
cheb_eval_e(&ak12_cs, 16.0/x-1.0, &c);
result->val = (1.25 + c.val) / sx;
result->err = c.err / sx;
result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
return GSL_SUCCESS;
}
}
double gsl_sf_bessel_I1(const double x)
{
EVAL_RESULT(gsl_sf_bessel_I1_e(x, &result));
}
