From dsmith@santafe.edu  Thu Feb 27 02:39:02 2003
From: dsmith@santafe.edu (dsmith@santafe.edu)
Date: Thu Feb 27 02:39:02 2003
Subject: [Rd] Alias does not label rows and columns correctly. (PR#2586)
Message-ID: <200302270138.h1R1cf35016559@pubhealth.ku.dk>

Alias does not label rows and columns correctly.  Instead of labeling the 
rows with the removed predictors, and the cols with the included predictors;
instead, it labels the columns with the first r predictors (where r is the
rank of the matrix) and the rows with the remaining predictors.

Here's an example:

                      > Y<-c(0,1,2)
                      > X1<-c(0,1,0)
                      > X2<-c(0,1,0)
                      > X3<-c(0,0,1)
                      
                      > alias(lm(Y ~ X1 + X2 + X3))
                      Model :
                      Y ~ X1 + X2 + X3
                      
                      Complete :
                         (Intercept) X1 X2
                      X3              1   


X1 and X2 are colliner, but alias reports X1 is collinear with X3.



The error is only in the assignment of names, the matrix alias prints
is correct.  Here's a fix (there may well be a better one, I'm new to R)

in function alias.lm, replace the line:

                # dimnames(beta12) <- list(dn[p1], dn[ -p1])                       

with:
                c<-object$coefficients                                             
                dimnames(beta12) <- list(names(c[!is.na(c)]), names(c[is.na(c)]))  



Derek



[Rd] Alias does not label rows and columns correctly. (PR#2586)
dsmith@santafe.edu