[R] term.formula error when updating an nls object

Hi, I'm getting an error that I don't understand when updating an nls object. Here is a toy example. dd - structure(list(Contrast = c(0.00376, 0.03759, 0.12782, 0.25564, 0.50376, 1), Response = c(0.29915, 6.13248, 29.01709, 30.0641, 29.46581, 27.67094)), .Names = c(Contrast, Response), class =

Re: [R] term.formula error when updating an nls object

Ken, You just need to wrap the rhs of your formula in I() to get around update()'s parsing of terms. m2 - update(m1, . ~ I(Rm * Contrast^ex/(Contrast^fx + sig^fx)), start = list(Rm = 30, sig = 0.05, ex = 3, fx = 3.1)) -Peter Ehlers Ken Knoblauch wrote:

Re: [R] term.formula error when updating an nls object

Thanks, I hadn't thought of that. It works fine, now. I'll look out for that in the future. Ken Quoting Peter Ehlers ehl...@ucalgary.ca: Ken, You just need to wrap the rhs of your formula in I() to get around update()'s parsing of terms. m2 - update(m1, . ~ I(Rm *