[SciPy-user] skew Gaussian distribution

elton wang ahala2000@yahoo....
Thu Aug 23 13:31:59 CDT 2007


I use R (http://cran.r-project.org/) for distribution
fitting. skewed-normal/skew-t or what ever
distributions. very ease to use.
I also have RDcom server/client
installed(http://sunsite.univie.ac.at/rcom/). So R can
be called in python as below (windows XP) (from
website above)

>>> from win32com.client import Dispatch
>>> sc=Dispatch("StatConnectorSrv.StatConnector")
>>> sc.Init("R")
>>> print(sc.Evaluate("2+2"))
4.0 # COMMENT- R can do arithmetic and can tell python
about it!
>>> 

--- David Goldsmith <David.L.Goldsmith@noaa.gov>
wrote:

> Ah, then I may be able to help you in two ways. 
> First, my Google search 
> turned up:
> 
> http://azzalini.stat.unipd.it/SN/
> 
> Visit the "very brief account" link thereon, but
> also note on the main 
> page the passage titled "A pioneer" which hints at a
> possible "physical" 
> basis for these distributions in nature; I didn't
> dig any deeper than 
> that, but it seems worthwhile to assess whether the
> family of 
> distributions he is discussing might "properly"
> represent your 
> experimental population.
> 
> Second, I used to work for an Astronomer/Applied
> Optics Engineer, and 
> was thus exposed, albeit superficially, to physical
> derivations of 
> empirical optical particle count distributions; I
> didn't learn enough to 
> help you, but he probably could - if you're
> interested, I can forward 
> you his email, or if your reticent about making a
> "cold" contact, I can 
> forward your email to him to see if he thinks he can
> help.
> 
> DG
> 
> Gary Pajer wrote:
> > On 8/23/07, *David Goldsmith*
> <David.L.Goldsmith@noaa.gov 
> > <mailto:David.L.Goldsmith@noaa.gov>> wrote:
> >
> >     Please educate me: what are a "skew" and
> "kurtotid"
> >     Gaussians?  (What I
> >     learned: Gaussians are - by definition -
> devoid of any
> >     higher-than-second moments; wouldn't
> (shouldn't) a "Gaussian" with
> >     higher-than-second moments be called something
> else entirely?)
> >
> >
> > Exactly.   So I could rephrase my question:  what
> is the name of the 
> > distribution that is similar to a normal
> distribution, but has a 
> > variable amount of skewness?   Or is such a
> distribution a special 
> > case of one of the many distributions in scipy?
> >
> > I *think*  the pdf of a "skew normal"  should be
> proportional to 
> > exp(-a*x**2 - b*x**3) but that comes from a quick
> google search.
> >
> > Better yet:  what I'm trying to do is simulate the
> spectrum of an 
> > optical emitter that I have.  The spectrum is
> nearly normal, but it is 
> > not symmetric.  I'm looking for a model
> distribution.  I started by 
> > looking for something quick and dirty.   If
> "quick" doesn't happen, I 
> > might actually have to figure out if there is
> already a 
> > theoretically-expected distribution for my case. 
> But in the meantime, 
> > quick and dirty still sounds good.
> >
> > That's the real question. 
> >
> > thanks for helping me express what I want  :)
> > -gary
> >
> >  
> >
> >     DG
> >
> >     Gary Pajer wrote:
> >     > Do any of the distributions in scipy.stats
> make a skew Gaussian?
> >     > Ditto,  a Gaussian with kurtosis?
> >     >
> >     > thanks,
> >     > -gary
> >     >
> >    
>
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