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passing parameters in optim()

3 messages · Nancy Lo, Thomas Lumley, Brian Ripley

Original
Nancy Lo
# 
Hi all,

I am using optim() to get estimate for parameter 'a' which will minimize
the output of lprob.catch(a) and I got an error message:
1,0.2,2,1,data.sf.mont))
Error in catch2.fun(k, f1, f2, a, b, A, B, R, n0, av, index.n) :
        Object "a" not found


Why wasn't the initial value of a=2 passed to catch2.fun() which was
called by lprob.catch()?

Thank you for your time.


Nancy


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Thomas Lumley
#
On Tue, 5 Feb 2002, Nancy Lo wrote:

            

      
      
      
    

        
The second argument to optim() must be a function of one variable
(possibly a vector variable), but
   lprob.catch(x, freq,1, 0.5,0.5, a,- 0.7, 1, -0.7,0.1, 1,0.2,2,1,data.sf.mont)
is a not a function at all.  How is optim() supposed to know that a=2,
rather than x=2, or data.sf.mont=2?

You probably wanted
 optim(2,function(a) {lprob.catch(x, freq,1, 0.5,0.5, a,- 0.7, 1, -0.7,0.1,1,0.2,2,1,data.sf.mont)})
assuming that all the other variables are defined.

	-thomas

Thomas Lumley			Asst. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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      Brian Ripley
    

    

      
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On Tue, 5 Feb 2002, Nancy Lo wrote:

        

            

      
      
      
    

        
fn: A function to be minimized (or maximized), with first
          argument the vector of parameters over which minimization is
          to take place. It should return a scalar result.

and a is not the first argument: you told it to optimze over x.