Re: Experimentian with Bayesian statistics

*To*: mathgroup at smc.vnet.net*Subject*: [mg45418] Re: Experimentian with Bayesian statistics*From*: poujadej at yahoo.fr (Jean-Claude Poujade)*Date*: Wed, 7 Jan 2004 01:09:09 -0500 (EST)*References*: <bt8o98$c1u$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

NA <nospam at here.com> wrote in message news:<bt8o98$c1u$1 at smc.vnet.net>... > Hi, > I'm trying to learn some basic Bayesian statistics with Mathematica but I'm > having trouble building up the probability formulae that I need. > > I tried to define > > depPr[x_,y_] := (Pr[x] depPr[y,x]) / Pr[y] > > but I don't even get an Out result (I thought it would have at least > redisplayed it with numerator over denominator) > > (I assumed by the way that I needed a different name for the function Pr{x > | y} vs the simple Pr{x}) > > > If I replace the ':=' with '=', then I just get a recursion error. > [...] This is an example of what you could do to prevent recursion : In[1]:=ClearAll[p]; p[a_[r_Integer(* event number *), n_Integer(* number of events *)],b_]:= p[b,a[r,n]]p[a[r,n]] / Sum[p[b,a[i,n]]p[a[i,n]],{i,1,n}]; Numeric example : In[2]:= p[a[1,2]] = 1/10; p[a[2,2]] = 9/10; p[b,a[1,2]] = 1/3; p[b,a[2,2]] = 1/60; In[3]:=p[a[1,2],b] Out[3]=20/29 In[4]:=p[a[2,2],b] Out[4]=9/29 hth --- jcp