code: function(df1, df2) {
           return {
              d: function(x, logp) { return df(df1, df2, logp)(x); },
              p: function(q, lowerTail, logp) {
                 return pf(df1, df2, lowerTail, logp)(q);
              },
              q: function(p, lowerTail, logp) {
                 return qf(df1, df2, lowerTail, logp)(p);
              },
              r: function() { return rf(df1, df2)(); }
           };
        }
docs: Returns an object representing an F distribution with
  given degrees of freedom `df1` and `df2`.  The object has
  properties `d`, `p`, `q`, `r`.
  ```
  fdistr(df1, df2).d(x, logp)            // same as df(df1, df2, logp)(x)
  fdistr(df1, df2).p(x, lowerTail, logp) // same as pf(df1, df2, lowerTail, logp)(x)
  fdistr(df1, df2).q(x, lowerTail, logp) // same as qf(df1, df2, lowerTail, logp)(x)
  fdistr(df1, df2).r()                   // same as rf(df1, df2)()
  ```
  @memberof f