[R] Substitute initial guesses of parameters in a function

[Duncan Murdoch]

On 03/12/2014 7:37 AM, philippe massicotte wrote:
> Hi everyone, I have a formula like this:
>
> f <- as.formula(y ~ p0a * exp(-0.5 * ((x - p1a)/p2a)^2))
>
> I would like to "dynamically" provide starting values for p0a, p1a, p2a. Is there a way to do it?

Just give a named vector of starting values.
>
> #Params estimates
> p <- c(12, 10, 1)

Should be p <- c(p0a = 12, p1a = 10, p2a = 1)
>
> # This is where I have difficulties
> mystart <- substitute(...)
>
> nls(formula = f, start = mystart)

Now start = p will work.  No need to mess with substitute.  (And no need 
to use as.formula on the very first line; that's already a formula.)

Duncan Murdoch
>
> Regards,
> Philippe
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