GammaIInv
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.
Examples
- Index y :=
Sequence(0,0.98,0.01)
- Variable a :=
[0.5, 1, 2, 5 ]
GammaIInv(y,a)
→
GammaIInv( Uniform(0,1), a, b )
is equivalent to Gamma(a,b)
.
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.
See Also
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