Functions and CALL Routines 
Returns the value of the noncentrality parameter of an F distribution.

x

is a numeric random variable.
Range: 
x 0 

ndf

is a numeric numerator degree of freedom
parameter.

ddf

is a numeric denominator degree of freedom
parameter.

prob

is a probability.
The FNONCT function returns the nonnegative
noncentrality parameter from a noncentral F distribution whose
parameters are x, ndf, ddf, and nc. If prob is greater than the probability from the central F distribution whose
parameters are x, ndf,
and ddf, a root to this problem does not exist. In this case
a missing value is returned. A Newtontype algorithm is used to find a nonnegative
root nc of the equation
where
where
I (. . .) is the probability from the
beta distribution that is given by
If the algorithm fails to converge to a fixed point,
a missing value is returned.
data work;
x=2;
df=4;
ddf=5;
do nc=1 to 3 by .5;
prob=probf(x,df,ddf,nc);
ncc=fnonct(x,df,ddf,prob);
output;
end;
run;
proc print;
run;
FNONCT Example Output
OBS x df ddf nc prob ncc
1 2 4 5 1.0 0.69277 1.0
2 2 4 5 1.5 0.65701 1.5
3 2 4 5 2.0 0.62232 2.0
4 2 4 5 2.5 0.58878 2.5
5 2 4 5 3.0 0.55642 3.0
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