y ~ . and y ~ -1 + .
are different parametrisations of the same model. The first has an
intercept and 3 columns for the factor and the second has no
intercept but 4 columns for the factor.
In SPLUS, (v3.3 for Windows and v4.5), calling summary
gives the results that the 2 fits have different values for Multiple
R-squared and the F-test for regression. (Other quantities such as s
are the same.) This appears to be caused by the fact that SPLUS
uses the formula for the no-intercept case when evaluating Multiple
R-squared for the second model.
(For the particular dataset that I had, the value of R-squared moved
form 0.66 to 0.98.)
What do people think of this behaviour? I much prefer no
information to misleading information and so I believe it would be
better if SPLUS output no values at all for these quantities in the no-intercept
case.
Robin Reed
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R J Reed R.J.Reed@warwick.ac.uk
Department of Statistics
University of Warwick
Coventry CV4 7AL
United Kingdom
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