[R] nls issue

[Mathew Brown]

Hello,

I'm trying to make a non-linear regression using the attached data and 
this model. When I run it I get the following message:

Error in nls(y ~ 1/(a + w * x), data = df, start = list(a = 1, w = 1),  :
   singular gradient



mod <- nls(y~1/(a+w*x),data=df,start=list(a=1,w=1),trace = TRUE)


Any idea what the problem is?

Cheers,
Mat