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delayed function assignment

• To: mathgroup at smc.vnet.net
• Subject: [mg88170] delayed function assignment
• From: leigh <leigh.pascoe at gmail.com>
• Date: Sun, 27 Apr 2008 04:57:43 -0400 (EDT)

Dear Mathgroup,

I am trying to integrate the pdf of a chi-square mixture distribution.
If I define the pdf as

pdf2[0] := .25
\!\(pdf2[x] :=  .5*\(\(1/2\^\(1/
        2\)\)\/Gamma[1/2]\) \(x\^\(1/2 - 1\)\) \[ExponentialE]\^\(\(-x
\)/
              2\) +  .25*\(1\/\(2*Gamma[1]\)\) \[ExponentialE]\^\(\(-x
\)/2\)\)

I can then obtaing the cumulative distribution function symbolically
as

In[14]:=\!\($B"i(Bpdf2[x] \[DifferentialD]x\)

Out[14]=\!\(\(-0.25`\)\ 2.718281828459045`\^\(\(-0.5`\)\ x\) + 0.5`\ \
Erf[0.7071067811865476`\ \@x]\)

I can get numerical values using for example

In[31]:=\!\(1 -  .25 - $B"i(B\_0\%12 pdf2[x] \[DifferentialD]x\)

Out[31]=0.000885691

However if I try to define this as a function of the statistic
obtained, say

\!\(cum2[x] := 1 -  .25 - $B"i(B\_0\%x pdf2[t] \[DifferentialD]t\)

Then

In[33]:=cum2[9]

Out[33]=cum2[9]

Doesn't evaluate. What should I do to obtain the value as output.

Thanks for your help

Leigh

• Follow-Ups:
  • Re: delayed function assignment
    • From: "W_Craig Carter" <ccarter@mit.edu>