[R] NLS mensagem error...

[Bernardo Rangel Tura]

Hi R-masters,

I have a problem with nls() and my research data. Look this example:



X2000<-c(1.205268,2.850695,5.100860,8.571610,15.324513,25.468599,39.623418,61.798856,91.470006,175.152509)
age<-c(37,42,47,52,57,62,67,72,77,82)
fit <- nls(X2000~R*exp(A*age),start=list(R=.1,A=.1))

Error mensage:

Error in nls(X2000 ~ R * exp(A * age), start = list(R = 0.1, A = 0.1)) : 
        singular gradient
In addition: Warning message: 
no finite arguments to min; returning Inf

How I fix this problem? Other command? 


Thanks in advance

Bernardo Rangel Tura, MD, MSc
National Institute of Cardiology Laranjeiras
Rio de Janeiro Brazil