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MathGroup Archive 1992

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Integration of Gaussians

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Integration of Gaussians
  • From: lsf at holmes.astro.nwu.edu (Sam Finn)
  • Date: Mon, 9 Mar 92 21:08:00 CST

Still a few bugs in the system . . . This is with the patch posted by
withoff at wri.com on 25 January 1992. It also happens on a next running
Mathematica version 2.0 (November 14 1991). 

Mathematica 2.0 for SPARC
Copyright 1988-91 Wolfram Research, Inc.
 -- Terminal graphics initialized -- 

In[1]:= f[x_,a_,sigma_] := Exp[-(x-a)^2/sigma^2]

In[2]:= Integrate[f[x,a,sigma],{x,-Infinity,Infinity}]

           2      2
          a /sigma                2         a
Out[2]= (E          Sqrt[Pi] sigma  Erf[----------] + 
                                        Abs[sigma]
 
                                             2          2      2
                                       3    a          a /sigma
>      a Abs[sigma] HypergeometricU[1, -, ------]) / (E          Abs[sigma])
                                       2       2
                                          sigma

In[3]:= Table[% /. sigma->1,{a,-1,1,0.5}]

Infinity::indet: Indeterminate expression 0. 1 ComplexInfinity encountered.

                                                   3
         -(E Sqrt[Pi] Erf[1]) - HypergeometricU[1, -, 1]
                                                   2
Out[3]= {-----------------------------------------------, 
                                E
 
>    0.778801 (-1.09128 - 0.668335 Sqrt[Pi]), Indeterminate, 
 
>    0.778801 (1.09128 + 0.668335 Sqrt[Pi]), 
 
>    0.367879 (0.757872 + 2.2907 Sqrt[Pi])}

In[4]:= N[%]

Out[4]= {-1.77245, -1.77245, Indeterminate, 1.77245, 1.77245}

In[5]:= ^D





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