[R] cbind results to original data frame

[Ingrid Tohver]

I have the following script, which gives me a prediction for each of  
my observations (> 49k), and subsets my data frame by site (n = 183):

ts <- (by(dem16,dem16['Site'],function(dat)
		try(predict(nls(Tw ~ mu + ((alpha - mu)/
  	                   (1 + exp(gamma*(B - Mean_air)))),
  	         data = dat,
  	         start = list(mu = 0.8, alpha = 21.8, gamma = 0.22, B =  
12.8),
		 algorithm = "port",
		 lower = list(0,0,0,0))))))

What I would like to do is apply the resulting "ts" list to my  
original data frame so I can perform a goodness of fit test. However,  
the resulting "ts" is a list only as long as the number of sites  
(183), so I can't force it to cbind to my original data frame with  
49,000 observations. How can I format ts to cbind with dem16 (the  
original)?

Thank you,
Ingrid