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MathGroup Archive 2006

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(again) common problem with FindMinimum and NIntegrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69509] (again) common problem with FindMinimum and NIntegrate
  • From: wtplasar at ehu.es
  • Date: Thu, 14 Sep 2006 06:56:28 -0400 (EDT)

Sorry, there was a missing line in the code (some data). It is correct 
as it appears below.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Hi everyone,

Some people have enquired in the past about how to avoid error 
messages similar to this one I get:

NMinimize::nnum: The function value 
Experimental`NumericalFunction[{Hold[bestchi[om, ol]], Block}, 
<<4>>, {None, None}] is not a number at {ol, om} = 
{1.5636149496419025`,0.08724393316032257`}

I have read the documentation and  tried to implement the 
recommendations posted at mathgroup, but to no avail.

Here is my code (it won't take much from your time):

ndat = {1.`, 2.`, 3.`, 4.`, 5.`, 6.`, 7.`, 8.`, 9.`};
Hobs = {69.`, 83.`, 70.`, 87.`, 117.`, 168.`, 177.`, 140.`, 202.`};
sH = {12.`, 8.3`, 14.`, 17.4`, 23.4`, 13.4`, 14.2`, 13.5`, 40.4`};
z = {0.09`, 0.17`, 0.27`, 0.4`, 0.88`, 1.3`, 1.43`, 1.53`, 1.75`};
H[x_, om_, ol_, H0_] := H0 Sqrt[om (1 + x)^3 + ol + (1 - om - ol)(1 + 
x)^2];
Hlist[om_, ol_, H0_, mylist_] := Thread[H[#, om, ol, H0]] &[mylist];
chisq[om_?NumericQ, ol_?NumericQ, H0_?
      NumericQ] := Switch[Head[N[#]], Real, #, Complex, 10^20] &[Module
[{vec1 = (Hobs - Hlist[om, ol, H0, z])^2, vec2 = (sH^2)}, Total
[vec1/vec2]]];
bestchi[om_?NumericQ, ol_?NumericQ] := -2*Log[NIntegrate[1/(3 Sqrt[2 
Pi])Exp[-
  Chop[(H0 - 73)]^2/18]Exp[-chisq[om, 
        ol, H0]/2], {H0, 71, 75}, WorkingPrecision -> 20]];
NMinimize[{bestchi[om, ol], 0.7 > om > 0 && ol > 0}, {
    om, ol}, Method -> {"RandomSearch"}];

I would appreciate someone posted a reply to show me how to fix it. 

Thanks a lot in advance,

Ruth Lazkoz


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