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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