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@alvgaona
Created December 8, 2020 13:11
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Zeroth Order Modified Bessel Function of the First Kind
x = 2;
ax = abs(x);
if (ax < 3.75)
y = x/3.75;
y = y*y;
ans = 1.0+y*(3.5156229+y*(3.0899424+y*(1.2067492 + y*(0.2659732+y*(0.360768e-1+y*0.45813e-2)))));
else
y=3.75/ax;
ans = (exp(ax)/sqrt(ax))*(0.39894228+y*(0.1328592e-1 ...
+y*(0.225319e-2+y*(-0.157565e-2+y*(0.916281e-2 ...
+ y*(-0.2057706e-1+y*(0.2635537e-1+y*(-0.1647633e-1 ...
+y*0.392377e-2))))))));
end
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