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MathGroup Archive 2004

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FindMaximum doesn't work?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47784] FindMaximum doesn't work?
  • From: suomesta at yahoo.com (Carol Ting)
  • Date: Mon, 26 Apr 2004 02:42:03 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi List,

I have one function which is defined only for a certain range of its
independent variable:

test[c_]:=((10-185c+((5^0.5)(20+19660c+6641c^2))^2)(-41-134c+(5^0.5)(20+19660c+6641c^2)))/(530604c)
1.4<=c<6.2

This function is decreasing in c so the maximum should be at 1.4. 
However, when the initial guess I give is greater than 2.6,
FindMaximum only returns the values at that point.

For example,

In[57]:=FindMaximum[test[c],{c,5}]
Out[57]:={-0.895005,{c->5.}}

But when I give 

In[58]:=FindMaximum[test[c],{c,2}]
Out[58]:={2.09973,{c->1.4}}

Then it works.

My program uses a While loop to generate piecewise functions (I only
put the piece containting the global maximum here).  The maximum
condition is needed to decide whether to terminate the loop so I
cannot always stop the execution and keep throwing in different
guesses.

Did I do anything wrong, or is this a bug?  Thanks a lot!

Carol


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