Hello,
I am trying to write some code for fitting negative binomial
distributions. When I came to writing the equation for the density
function I remembered that in Venables and Ripley's MASS book for R and
Splus that they use a shape parameter 'Theta', which must be specified
and as far as I can remember defines the variance mean relationship - I
assumed this was a three parameter representation of the distribution
(this maybe where my confusion arises). But everywhere else I look I
can only find a two parameter representation typically the
generalisation of the pascal distribution.
If anyone has any information on the density function for the negative
binomial used in the MASS library I would be very grateful.
Best Regards,
Colin.
Colin Millar,
Marine Laboratory,
Aberdeen.
|