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Package gammp (in gammp.i) -

Index of documented functions or symbols:

betai

DOCUMENT betai(a, b, x)
  return I_x(a,x) = int[0 to x]{ du * u^(a-1)*(1-u)^(b-1) } / beta(a,b)
  the incomplete beta function

  betai(a,b,x) = 1 - betai(b,a,1-x)

  Note that Student's t-distribution is
    A(t|nu) = 1 - betai(0.5*nu,0.5, nu/(nu+t^2))
  The F-distribution is
    Q(F|nu1,nu2) = betai(0.5*nu2,0.5*nu1, nu2/(nu2+F*nu1))

SEE ALSO: gammp, gammq, ln_gamma,

gammp

DOCUMENT 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).

SEE ALSO: gammq, betai, ln_gamma,

gammq

DOCUMENT 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).

SEE ALSO: gammp, betai, ln_gamma,