Hi Claire, More generally, too, it is not surprising to find that two codings differ in collinearity (e.g. treatment coding vs. contrast/sum coding). Which coding you should use depends on (a) what hypothesis you want to test and (b) if you need to reduced collinearity (b/c you need reliable estimates of effect direction and/or effect shape, since otherwise you could simply use model comparison).
florian On Mon, Apr 20, 2009 at 6:16 AM, Matthew Roberts <[email protected]>wrote: > Are you sure that the numeric values are the same in each case? When R > converts factor() to numeric(), it take the numerical factor id rather > than the name. To avoid this do: > > numeric.condition.number <- > as.numeric(as.character(factor.condition.number)) > > Hope this helps, > > Matthew > > * Claire Delle Luche <[email protected]> [2009-04-20 > 10:41:58 +0200]: > > > Dear R-users, > > > > I am running a mixed effect model on a written corpus. > > When I check for collinearity, I get a value of 35 for condition number > when my predictors are entered as names then transformed as numeric (the > values are 1 and 2 for two level predictors after the transormation). > > However, when I enter the predictors as factors and assign levels of 0 > and 1 instead of names (and convert them as numeric), I get a condition > number of 12. > > > > For the same data, depending on how I code the predictors, I either have > moderate or important collinearity. What shall I do? > > Which coding is more acceptable? > > > > Thanks very much in advance. > > > > Yours, > > > > Claire Delle Luche > > Laboratoire Dynamique du Langage > > 14, avenue Berthelot > > 69 007 Lyon > > France > > > > _______________________________________________ > > R-lang mailing list > > [email protected] > > http://pidgin.ucsd.edu/mailman/listinfo/r-lang > > > > -- > Matthew A. J. Roberts > Department of Psychology, > University of Edinburgh, > 7 George Square > EH8 9JZ > +44 (0)131 6511302 > -- > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > > _______________________________________________ > R-lang mailing list > [email protected] > http://pidgin.ucsd.edu/mailman/listinfo/r-lang >
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