On Nov 14, 2011, at 6:11 AM, Michele Mazzucco wrote:
Hello David,
thanks for your answer.
I have done as you told me, however the fit is very poor, much worse
than that obtained from using the whole dataset (without upper bound).
Any idea?
Counter questions in the absence of data:
??? Is there a reason from domain specific knowledge and theory to
expect that the procedure you are attempting should be correct?
??? Why would you want to exclude data?
??? Why are you not looking for more general tutorials (such as the
one by Ricci) rather than asking what is as yet an open-ended question
on fitting methods that surely does not admit an answer easily
provided on a mailing list?
--
David.
Thanks,
Michele
On Nov 4, 2011, at 8:56 PM, David Winsemius wrote:
On Nov 3, 2011, at 7:54 AM, Michele Mazzucco wrote:
Hi all,
I am trying to fit a distribution to some data about survival times.
I am interested only in a specific interval, e.g., while the data
lies in the interval (0,...., 600), I want the best for the
interval (0,..., 24).
I have tried both fitdistr (MASS package) and fitdist (from the
fitdistrplus package), but I could not get them working, e.g.
fitdistr(left, "weibull", upper=24)
Error in optim(x = c(529L, 528L, 527L, 526L, 525L, 524L, 523L,
522L, 521L, :
L-BFGS-B needs finite values of 'fn'
In addition: Warning message:
In dweibull(x, shape, scale, log) : NaNs produced
Am I doing something wrong?
You didn't supply data to test, but shouldn't you supply a lower
bound if you want to fit "weibull"? It is, after all, bounded at 0.
left <- c(529L, 528L, 527L, 526L, 525L, 524L, 523L, 522L, 521L,
50*runif(100))
fitdistr(left, "weibull", upper=24)
Error in optim(x = c(529, 528, 527, 526, 525, 524, 523, 522, 521,
18.3964251773432, :
L-BFGS-B needs finite values of 'fn'
In addition: Warning message:
In dweibull(x, shape, scale, log) : NaNs produced
fitdistr(left, "weibull", upper=24, lower=0.5)
shape scale
0.58195013 24.00000000
( 0.04046087) ( 3.38621367)
Thanks,
Michele
p.s. I have seen similar posts, e.g., http://tolstoy.newcastle.edu.au/R/help/05/02/11558.html
, but I am not sure whether I can apply the same approach here.
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
David Winsemius, MD
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
