Re: [R] Interpreting model matrix columns when using contr.sum

2009-01-25 Thread Gang Chen
-Original Message- >> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On >> Behalf Of Douglas Bates >> Sent: January-25-09 10:49 AM >> To: Gang Chen >> Cc: R-help >> Subject: Re: [R] Interpreting model matrix columns w

Re: [R] Interpreting model matrix columns when using contr.sum

2009-01-25 Thread John Fox
ct.org [mailto:r-help-boun...@r-project.org] On > Behalf Of Douglas Bates > Sent: January-25-09 10:49 AM > To: Gang Chen > Cc: R-help > Subject: Re: [R] Interpreting model matrix columns when using contr.sum > > On Fri, Jan 23, 2009 at 4:58 PM, Gang Chen wrote: > > With the foll

Re: [R] Interpreting model matrix columns when using contr.sum

2009-01-25 Thread Douglas Bates
On Fri, Jan 23, 2009 at 4:58 PM, Gang Chen wrote: > With the following example using contr.sum for both factors, > >> dd <- data.frame(a = gl(3,4), b = gl(4,1,12)) # balanced 2-way >> model.matrix(~ a * b, dd, contrasts = list(a="contr.sum", b="contr.sum")) > > (Intercept) a1 a2 b1 b2 b3 a1:

[R] Interpreting model matrix columns when using contr.sum

2009-01-23 Thread Gang Chen
With the following example using contr.sum for both factors, > dd <- data.frame(a = gl(3,4), b = gl(4,1,12)) # balanced 2-way > model.matrix(~ a * b, dd, contrasts = list(a="contr.sum", b="contr.sum")) (Intercept) a1 a2 b1 b2 b3 a1:b1 a2:b1 a1:b2 a2:b2 a1:b3 a2:b3 11 1 0 1