Hi John, thanks for your reply. Your answer is basically what the
documentation describes. But, it still leaves me with question marks
in my head.
Let me ask differently. How do I construct the the red curve in the
second image? Parameters here are: Shape = 1 and Scale = 1. BTW,
shouldn't be the "scale" box in the second image be called "rate"?
Thanks again,
Christian
On Dec 19, 2007 4:46 AM, John Maddock
Christian Henning wrote:
Hi there, the documention of the gamma distribution talks about two different forms. How can can generate the second one with shape=1 and scale=1? I know how to get the first form:
boost::math::gamma_distribution<> dist( 1, 1 );
I don't see how to get the second one?
Right, the distribution takes two parameters: shape and *scale*, so the construction is always:
boost::math::gamma_distribution<> d(myshape, myscale);
If instead you have parameters shape and *rate* then it's constructed as:
boost::math::gamma_distribution<> d(myshape, 1/myrate);
Or as noted in the docs "Therefore to construct a Gamma Distribution from a rate parameter, you should pass the reciprocal of the rate as the scale parameter."
In other words the a rate parameter is simply the reciprocal of the scale, and vice versa.
Any clearer?
HTH, John.
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