[SciPy-user] noncentral F distribution?
Neal Becker
ndbecker2@gmail....
Wed May 27 18:59:36 CDT 2009
Robert Kern wrote:
> On Wed, May 27, 2009 at 18:47, Neal Becker <ndbecker2@gmail.com> wrote:
>
>> Thanks! Just one more. What are dfn, dfd? The doc calls them "shape
>> parameters", but I don't know what that means.
>
> A "shape parameter" is a generic term for any parameter that is not a
> location or scale parameter. In this case, dfn is the parameter for
> the degrees of freedom in the numerator of the expression for the F
> distribution (whether it is noncentral or not) and dfd is the degrees
> of freedom in the denominator.
>
I think I get it now. I had assumed that you must first construct an
instance of a ncf object (specifying parameters) and then call the cdf
method (specifying x).
Now I see that you simply call:
ncf.cdf (x, dfn, dfd, nc)
Is that correct?
BTW, I was confused by:
scipy.stats.ncf(momtype=1, a=None, b=None, xa=-10.0, xb=10.0, xtol=1e-14,
badvalue=None, name=None, longname=None, shapes=None, extradoc=None)
which is the first thing seen in the doc. It appears to be the constructor
declaration? These parameters don't seem to be defined anywhere.
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