macro
Fcdf F a b cdf

#This function reports the right tail area of the F dist'n
#with a numerator and b denominator degrees of freedom.

#F is the input F value
#a and b are num and denom df respectively
#cdf is the resulting right tail area

#This macro must have access to the IncBeta macro

#Example calling statement:
#    mtb> %fcdf 2.8 4 28 k1
#Answer is cdf = 0.0449964

#by PGMathews 15 March 2001 
#Copyright (c) March 2001 by PGMathews All rights reserved

mconstant F a b cdf p q x

let p=b/2
let q=a/2
let x=b/(b+a*F)
%IncBeta x p q cdf
print cdf

endmacro