[R] a question regarding updating formulas with coefficients
Jarrett Byrnes
byrnes at msi.ucsb.edu
Thu Aug 12 00:03:19 CEST 2010
I have formulae with coefficents that I would like to update. However, I get some strange results. For example, see the following:
For the formula y ~ d+ 3*r+t I want to add a variable p, so
> update(y~d+0*r+t, .~.+p)
produces
y ~ d + t + p - 1
If the coefficient is not 0, but rather, something else - say, 3, I get the following:
> update(y~d+3*r+t, .~.+p)
Error in terms.formula(tmp, simplify = TRUE) :
invalid model formula in ExtractVars
>
Is there a way to do this, or a different call I should be trying?
-Jarrett
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