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