I don't know what else is wrong, but do you really want
a shape parameter equal to 28? gamma(28) is about 10^28.
That's not a model I would trust.
-Peter Ehlers
On 2010-04-15 9:37, Asif Wazir wrote:
Dear all
i want to estimated the parameter of the gamma density(a,b,d)
f(x) = (1/gamma(b)*(a^b)) * ((x-d)^(b-1)) * exp{-(x-d)/a)} for x>d
f(x) = Age specific fertility rate
x = age
when i run this in R by usling nls()
gamma.asfr<- formula(asfr ~ (((age-d)^(b-1))/((gamma(b))*(a^b)))*
exp(-((age-d)/a)))
gamma.asfr1<- nls(gamma.asfr, data= asfr.aus, start = list(b = 28, a = 1,
d= 0.5), trace = TRUE)
error: Error in numericDeriv(form[[3L]], names(ind), env) : Missing value
or an infinity produced when evaluating the model
when I use plinear algoritm, and run this
gamma.asfr1<- nls(gamma.asfr, data= asfr.aus, start = list(b = 28, a = 1,
d= 0.5), trace = TRUE, algorithm="plinear")
error: number of iterations exceeded maximum of 50
then i fix the iteration and minFactor even then its can't work
gamma.asfr1<- nls(gamma.asfr, data= asfr.aus, start = list(b = 28, a = 1,
d= 0.5), trace = TRUE, algorithm="plinear", nls.control(maxiter=500,
minFactor=0.000001))
error: Missing value or an infinity produced when evaluating the model
Can any body tell the problem, where i am doing wrong
thanks in advanc
..
Muhammad Asif Wazir
Ph.D student
Institut für Statistik und Decision Support Systems (ISDS).
University of Vienna, Austria
cell: 00436509092298
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--
Peter Ehlers
University of Calgary
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