Date: Fri, 16 Apr 2010 18:14:08 -0400 (EDT) From: Allin Cottrell <cottrell(a)wfu.edu&gt; Subject: Re: [Gretl-devel] NA and nan: next steps To: Gretl development <gretl-devel(a)lists.wfu.edu&gt; Message-ID: <Pine.A41.4.58.1004161812050.2326900(a)f1n11.sp2net.wfu.edu&gt; Content-Type: TEXT/PLAIN; charset=US-ASCII On Sat, 17 Apr 2010, Sven Schreiber wrote: ->OK, they may make _some_ distinction, but if they evaluate 0*NA as- ->NA (as we've heard) then they are not doing it right. ->Allin Except if 0 is a dummy variable. In that case 0*NA = NA., 0 is not really zero in ordinal data--it's arbitrary and just indicates a category. Otherwise recoding the dummy variables changes the effective data set and lead to unexpected results. If 0 is really zero in the cardinal sense then gretl handles this correctly and R/Octave do not. If 0 is a categorical variable gretl gets it wrong and Octave/R get it right. One solution would be to declare dummy variables as factors (like Jeff Racine does in his semiparametric models) so that the handling of the interactions could be right in both instances. I like what gretl does for cardinal data. But I'm not sure this is what I would want for ordinal/categorical data. Lee