GammaIInv(y, a, b)
Returns the inverse of the incomplete Gamma function. The function returns the value x such that
- GammaI(x, a, b) = y
«a» is the shape parameter, «b» is an optional scale factor that defaults to 1.
GetFract(Gamma(a, b), y) is an approximation to GammaIInv(y, a, b), obtained via sampling. The former is subject to sampling error, with less error at increased sample sizes, whereas by using GammaIInv directly, sampling error is avoided entirely.
- Use File → Add Library... to add this library
Index y := Sequence(0,0.98, 0.01)
Variable a := [0.5, 1, 2, 5]
GammaIInv(y, a) →
GammaI(12, 5, 2) → 0.7149
GammaIInv(0.7149, 5, 2) → 12