R help - May 2009 - model fitting using by(): how to get fitted values?

Hi all,

I'm doing nonlinear regressions on data with several factors. I want to fit
say a logistic curve with different parameter values for each factor level. So
I'm doing something like:

tmp <- by( myData, list(myFactor1, myFactor2), function(x) nls(...) )

It works fine. However, I could not find an easy way to retrieve fitted values.
I can use fitted() on each element of tmp, but that gives me as many vectors as
there are combinations of factor levels.

I was thinking of using by() again, but I can't figure out how to write it
properly.

Any ideas?


Thanks a lot,

Xavier

On 06/05/2009 8:22 AM, xavier.chardon at free.fr wrote:
> Hi all,
> 
> I'm doing nonlinear regressions on data with several factors. I want to
fit say a logistic curve with different parameter values for each factor level.
So I'm doing something like:
> 
> tmp <- by( myData, list(myFactor1, myFactor2), function(x) nls(...) )
> 
> It works fine. However, I could not find an easy way to retrieve fitted
values. I can use fitted() on each element of tmp, but that gives me as many
vectors as there are combinations of factor levels.
I think lapply() (or maybe sapply) will do what you want.  I haven't 
tried this, but it should be something like

lapply(tmp, fitted)

Duncan Murdoch
> 
> I was thinking of using by() again, but I can't figure out how to write
it properly.
> 
> Any ideas?
> 
> 
> Thanks a lot,
> 
> Xavier
> 
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