Re: [boost] Re: lognormal_distribution documentation error

From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2001-11-12 14:39:20

Brad Hanson wrote:
> It looks to me the way the lognormal_distribution
> constructor is written that the mean and sigma arguments are
> in fact the mean and standard deviation of the lognormal
> distribution, as opposed to the mean and standard deviation
> of the underlying normal distribution.

Hm... Yes.

>  The mean and sigma in
> p(x) should be the mean and standard deviation of the
> underlying normal distribution. I also think that
> sqrt(2*pi*sigma) should be sqrt(2*pi) in p(x).

This is definitely true.

> Here's how I would modify the documentation of the
> lognormal_distribution members:

I've fixed the documentation.

However, I'm wondering whether this is actually the
right design decision:  It appears that people will
likely want to specify the mean and sigma of the
underlying normal distribution, and don't care too much
about mean and sigma of the lognormal distribution.

Do we need both options?

Also, the default values (mean = 0, sigma = 1)
given in my code for the lognormal distribution do not
make sense (mean = 0 leads to log(0) which is undefined).

Jens Maurer