From sims at Princeton.EDU  Thu Jan 12 16:45:20 2006
From: sims at Princeton.EDU (sims@Princeton.EDU)
Date: Thu, 12 Jan 2006 16:45:20 +0100 (CET)
Subject: [Rd] follow-up on qr.coef bug (PR#8478)
Message-ID: <20060112154520.EA32720799@slim.kubism.ku.dk>

This is a multi-part message in MIME format.
--------------090308090600080800090200
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

The bug I submitted yesterday (It's not entered in the bug data base, so 
I have no ID for it) included a suggested fix that
is not correct.  It worked for the examples I gave because there was no 
pivoting in fact, or only pivot permutations that were
idempotent.   A correction that works in general on the examples I gave 
makes these two changes in qr.coef():

        ## coef[qr$pivot, ] <- .Call("qr_coef_cmplx", qr, y, PACKAGE = 
"base")[1:p]
        coef[qr$pivot,] <- .Call("qr_coef_cmplx", qr, y, PACKAGE = 
"base")[1:p,]

        ##coef[qr$pivot,] <- .Call("qr_coef_real", qr, y, PACKAGE = 
"base")[1:p]
        coef[qr$pivot,] <- .Call("qr_coef_real", qr, y, PACKAGE = 
"base")[1:p,]

I'm not sure why the [1:p,] on the right is needed.  For my examples, it 
works without this extraction operation, but maybe there is some case in 
which the output of qr_coef_real or qr_coef_cmplx could have more than p 
rows.



--------------090308090600080800090200
Content-Type: text/x-vcard; charset=utf-8;
 name="sims.vcf"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
 filename="sims.vcf"

begin:vcard
fn:Chris Sims
n:Sims;Chris
org:Princeton University;Department of Economics
adr:;;Fisher Hall;Princeton;NJ;08544-1021;USA
email;internet:sims at princeton.edu
tel;work:609 258 4033
tel;fax:609 258 6419
x-mozilla-html:FALSE
url:http://www.princeton.edu/~sims
version:2.1
end:vcard


--------------090308090600080800090200--



[Rd] follow-up on qr.coef bug (PR#8478)
sims@Princeton.EDU