Is your design of full rank? If you have not already done this, I
might try the same model (possibly replacing "as.ordered(q23p)" with a
vector I knew was numeric) in "lm". If "lm" says it is singular, you
need to simplify the model by deleting some terms. The "singular.ok"
option in "lm" will delete terms and fit something.
Alternatively, do you get the same error with models, e.g.:
polr(as.ordered(q23p)~1, data=newdatap)
polr(as.ordered(q23p)~ q29p+q30ap+q30bp+q30cp+q31ap+q31bp+q31cp+
q31dp+q32p+q33p+segmentp+ htypep+newtypep+tptimedp, data=newdatap)
hope this helps. spencer graves
C. Spanou wrote:
Hello Splus users, I am using the function polr in library(MASS).Below
are the the command I use
polr(as.ordered(q23p)~
timep+dayp+sitep+rq2p+typep+rq4ap+rq4bp+vehicp+passp+survp+sex1p+sex2p+age1p+age2p+perp+q3p+q4p+q5p+q6p+q7p+q8a2p+q8b2p+
q8c2p+q9p+ q10p+q11p+q12p+q13p+
q14p+q15p+q16p+q17p+q18p+q19p+q20p+q21ap+q21bp+q22p+q23p+q24p+q25p+q26p+q27p+q28p+
q29p+q30ap+q30bp+q30cp+q31ap+q31bp+q31cp+ q31dp+q32p+q33p+segmentp+
htypep+newtypep+tptimedp, data=newdatap)
But I am getting the following warning message singularity encountered
in: nlminb.1(temp, p, liv, lv, objective, gradient, bounds, scale)
Can anyone suggest what it could be wrong?
Any hints will be appreciated
Thank you
Charis
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