Re: Statistical packages
- To: mathgroup at yoda.physics.unc.edu
- Subject: Re: Statistical packages
- From: David Withoff <withoff>
- Date: Tue, 29 Sep 1992 08:25:16 -0500
> In[1]:= <<Statistics`Master`
>
> In[2]:= PDF[NormalDistribution[0,1],x]
>
> PDF::shdw: Warning: Symbol PDF appears in multiple contexts
> {Statistics`Common`DistributionsCommon`, Global`}; definitions in context
> Statistics`Common`DistributionsCommon`
> may shadow or be shadowed by other definitions.
>
> Out[2]= PDF[NormalDistribution[0, 1], x]
>
> What did go wrong?
This problem can be fixed by adding the following lines to
Statistics`Master`, which were missing in V2.0 :
DeclarePackage["Statistics`Common`DistributionsCommon`",
{"CDF", "CharacteristicFunction", "Domain", "PDF", "QuantileQ"}]
or, in Mathematica :
In[2]:= << Statistics`Master`
In[3]:= DeclarePackage["Statistics`Common`DistributionsCommon`",
{"CDF", "CharacteristicFunction", "Domain", "PDF", "QuantileQ"}]
Out[3]= Statistics`Common`DistributionsCommon`
In[4]:= PDF[NormalDistribution[0,1],x]
1
Out[4]= ----------------
2
x /2
E Sqrt[2 Pi]
> In[1]:= !!alku.m
> <<Statistics`ContinuosDistributions`
> <<Statistics`NormalDistribution`
>
> In[1]:= <<alku.m
>
> SetDelayed::write:
> Tag ChiSquareDistribution in Domain[ChiSquareDistribution[___]]
> is Protected.
This is caused by effectively loading Statistics`NormalDistribution`
twice (it is included in Statistics`ContinuosDistributions`).
Special provisions must be made to allow these packages to be loaded
a second time without error. Usually, these provisions consist of
unprotecting and clearing all of the symbols in the package. The V2.0
statistics packages are not set up this way.
A common alternative is to use Needs[package] rather than Get[package]
(or <<package ). Needs is much like Get except that Needs checks to see
if the context associated with the package is in the $Packages list
before loading the package, thereby avoiding loading a package that has
already been loaded.
Dave Withoff
withoff at wri.com