[R] how to define the bound between parameters in nls()

[Jinsong Zhao]

Hi there,

I have read the help page of nls(), there is lower or upper for defining 
the bounds of parameters. For example,

nls(y ~ 1-a*exp(-k1*x)-(1-a)*exp(-k2*x), data=data.1, start=list(a=0.02, 
k1=0.01, k2=0.0004), upper=c(1,1,1), lower=c(0,0,0))

I hope to define k1 > k2, but I don't find a way.

Any suggestions will be really appreciated.

Regards,
Jinsong