[R] problem in fitting model in NLS function

[muzammil786]

Dear David,

I am having a similar problem on this data (given below). I have tried
several starting values for a and b, but it is consistently giving me:

*fm <- nls(y~f(x,a,b), data.frame(x,y), start=c(a=1,b=1))
Error in numericDeriv(form[[3L]], names(ind), env) : 
  Missing value or an infinity produced when evaluating the model*

The function f(x,a,b) is defined here:
*f <- function(x,a,b) {a * I(x^b)} *

The data is given here:

*      x   y
1  1980   1
2  1981   1
3  1982   1
4  1983   3
5  1984   3
6  1985   5
7  1986   8
8  1987   8
9  1988   9
10 1989  12
11 1990  15
12 1991  24
13 1992  33
14 1993  44
15 1994  62
16 1995  68
17 1996  81
18 1997  87
19 1998 102
20 1999 114
21 2000 123
22 2001 135
23 2002 144
24 2003 158
25 2004 172
26 2005 188
27 2006 197
28 2007 224
29 2008 234
30 2009 254
31 2010 278
32 2011 312
33 2012 317*

I shall be grateful if you could guide me what's wrong here.

Cheers.
Muzammil



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