[R] forecasting with non-linear models

[Елена Белых]

Dear colleagues!
Is it possible to make predictions in R?
there is an exponential relationship detween y and x
x<-c(0.001,0.003,0.01,0.16,0.3,0.7,0.9)
y<-c(38.8,41.5,44.2,27,26.9,6.9,3)
f<-function(x,a,b){a*exp(b*x)}
fm<-nls(y~f(x,a,b), start=c(a=1,b=1))

How one can predict x when y=10 and is it possible to calculate standard 
error of x?
The task is equal to function ED in drc package, but it use logistic 
regression only.

Best regards,
Elena.

--
daryd at rambler.ru.