[R] System of logistics Equations

Bernardo Rangel Tura tura at centroin.com.br
Fri Feb 20 11:19:40 CET 2009

Hi R-masters

I need yours help about a problema in one of may ongoing researchers.

In my research the subjects (20 in total) answer 60 questions (20 type
G, 20 type S and 20 type P).

Which questions is classified about 3 factor (2 level each) and the
subject score with 2 scale (not integer value is possible but rare): Val
range -7 to 7 and other Car range 1 to 7.

This a code to fake database of research 


In my hypothesis:

logit(Sti=="G") ~ SP+AG+Mer+Car+Val+SP*Car+Mer*Val+AG*Val + errorG

logit(Sti=="S") ~ SP+AG+Mer+Car+Val+SP*Car+Mer*Val+AG*Val + errorS

logit(Sti=="P") ~ SP+AG+Mer+Car+Val+SP*Car+Mer*Val+AG*Val + errorP

I test and the 3 terms of error (errorG,errorS,errorP) is correlated.

So I think useful adjust a system of logistic equations to tread the 3
equations and in same time to obtain estimatives of effects and
uncorrelated error terms.

The systemfit package fit linear system and non-linear system but is
possible adjust a logistic system in R?

Thanks in advance

Bernardo Rangel Tura, M.D,MPH,Ph.D
National Institute of Cardiology

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