The Fisher distribution, its complement, and inverse.
The F density function (also known as Snedcor's density or the variance ratio density) is the density of x = (u1/df1)/(u2/df2), where u1 and u2 are random variables having χ2 distributions with df1 and df2 degrees of freedom, respectively.
fisherCDF returns the area from zero to x under the F density function. The complementary function, fisherCDFR, returns the area from x to ∞ under the F density function.
The inverse of the complemented Fisher distribution, invFisherCDFR, finds the argument x such that the integral from x to infinity of the F density is equal to the given probability y.