## functions in gammp.i - g

gammp
```
gammp(a, x)
or gammp(a, x, q, lg)

return P(a,x) = int[0 to x]{ du * u^(a-1)*exp(-u) } / gamma(a)
optionally return Q(a,x) = 1-P(a,x) and ln(gamma(a))

Note that erf(x)=gammp(0.5,x^2) and erfc(x)=gammq(0.5,x^2)
Also P(chi2|nu)=gammp(0.5*nu,0.5*chi2)
and Q(chi2|nu)=gammq(0.5*nu,0.5*chi2)
are the probabilities that an observed chi-square be less than
or greater than (P or Q) chi2 when there are nu degrees of freedom
(terms in the chi-square sum).

Interpreted function, defined at i/gammp.i   line 14

```

gammq
```
gammq(a, x)
or gammq(a, x, p, lg)

return Q(a,x) = 1 - int[0 to x]{ du * u^(a-1)*exp(-u) } / gamma(a)
optionally return P(a,x) = 1-Q(a,x) and ln(gamma(a))

Note that erf(x)=gammp(0.5,x^2) and erfc(x)=gammq(0.5,x^2)
Also P(chi2|nu)=gammp(0.5*nu,0.5*chi2)
and Q(chi2|nu)=gammq(0.5*nu,0.5*chi2)
are the probabilities that an observed chi-square be less than
or greater than (P or Q) chi2 when there are nu degrees of freedom
(terms in the chi-square sum).

Interpreted function, defined at i/gammp.i   line 50

```