[R] Problem with terms of the form (a >1) and subsetting of a terms object

[Niels Richard Hansen]

I have the following problem

mydata <- data.frame(a=1:3)
form <- ~ (a>1) - 1
model.matrix(form,mydata)

  a > 1FALSE a > 1TRUE
1          1         0
2          0         1
3          0         1
...

However

model.matrix(update(terms(form)[1],~.-1),mydata)

   (Intercept) a > 1 - 1TRUE
1           1             1
2           1             1
3           1             1
...

Taking

terms(form)[1]

extracts the formula with only the first term, but the parentheses
are thrown away, and after the update, I get a different formula.
Is that supposed to be so?

Thanks, Niels

-- 
Niels Richard Hansen                     Web:   www.math.ku.dk/~richard	
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