On Mon, 28 Apr 2008, Bin Yue wrote:
Dear friends:
I am a new R user, and not very good at statistics and maths
I find it difficult to find the minimum of this item:
((p*(b-1)-1)*(p+1)^(b-1)+1)/p^2
It seems that the method optim can find the minimum. I tried several
times , but R constanly tells that " failure to find b or p"
Would you please give some suggestions?
1) follow the posting guide
2) "provide commented, minimal, self-contained, reproducible code"
3) be sure optim 'understands' what the domain of your function is. You do
this by choosing explicit constraints or a suitable reparameterization.
4) make sure you understand your function well enough to carry out 3. You
do this by plotting your function and/ or plugging in some trial values.
Or you do some actual math and try to figure out if there are
multiple minima, places where derivatives do not exist, and so on. If
there are such troublesome issues, you will need to sort them out before
optim has a chance at finding a useful answer.
HTH,
Chuck
Thanks in advance.
Best wishes,
Bin Yue
-----
Best regards,
Bin Yue
*************
student for a Master program in South Botanical Garden , CAS
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
