/* Value of a blob --------------------------------------------------------- */
double kaiser_value(double r, double a, double alpha, int m)
{
double rda, rdas, arg, w;
rda = r / a;
if (rda <= 1.0)
{
rdas = rda * rda;
arg = alpha * sqrt(1.0 - rdas);
if (m == 0)
{
w = bessi0(arg) / bessi0(alpha);
}
else if (m == 1)
{
w = sqrt (1.0 - rdas);
if (alpha != 0.0)
w *= bessi1(arg) / bessi1(alpha);
}
else if (m == 2)
{
w = sqrt (1.0 - rdas);
w = w * w;
if (alpha != 0.0)
w *= bessi2(arg) / bessi2(alpha);
}
else if (m == 3)
{
w = sqrt (1.0 - rdas);
w = w * w * w;
if (alpha != 0.0)
w *= bessi3(arg) / bessi3(alpha);
}
else if (m == 4)
{
w = sqrt (1.0 - rdas);
w = w * w * w *w;
if (alpha != 0.0)
w *= bessi4(arg) / bessi4(alpha);
}
else
REPORT_ERROR(ERR_VALUE_INCORRECT, "m out of range in kaiser_value()");
}
else
w = 0.0;
return w;
}
double bessi4(double x)
{
return (x == 0) ? 0 : bessi2(x) - ((2 * 3) / x) * bessi3(x);
}
