Re: [R] Problem with systemfit 0.7-3 and transformed variables

From: Mikko Pakkanen <mikko.pakkanen_at_helsinki.fi>
Date: Thu 26 May 2005 - 02:25:12 EST


> We did not notice this shortcoming of systemfit() so far. Unfortunately,
> I
> don't have the time in the next few days to look into the code and figure
> out
> how to enable transformed variables. I suggest that you either create
> transformed variables by hand or you modify the systemfit code to enable
> this
> and send us the patch. I prefer the second :-) (that's the philosophy of
> open-source software like R: useRs become developeRs).

Luckily, I had some time to check the code. Debugger revealed that the problems are caused by the model.frame function which is used to compile the '$data' data frame. I don't need that data frame so much, so I just substituted model.frame with model.matrix which apparently doesn't cause this error with transformed variables. However, I tuned it a bit further, so that it should still return an identical '$data' data frame, despite the modification.
I've only tested this with my example and it appears to be OK. Still, I think this should be considered a "quick & dirty" fix -there are probably better ways to do it. But, I hope it gives the idea. Here's my attempt:

mikko@briscoe R $ diff -u systemfit.R systemfit-patched.R --- systemfit.R 2004-11-26 11:17:36.000000000 +0200 +++ systemfit-patched.R 2005-05-25 18:55:55.568944699 +0300 @@ -624,7 +624,11 @@

     Terms <- terms( eqns[[i]], data = data)
     m$formula <- Terms
     m <- eval(m, parent.frame())

- datai <- model.frame(Terms, m)
+ resp <- model.extract(m, "response") + ## using model.matrix instead of model.frame, need to get the output variable separately
+ datai <- data.frame(cbind(resp, (model.matrix(Terms, m))[,-1])) + ## I guess there's a better way to extract the name of the output variable?
+       names(datai)[1] <- as.character(terms(eqns[[i]]))[2]
     if(method=="2SLS" | method=="3SLS") {
       #datai <- cbind( datai, model.frame( instl[[i]] ))
       # the following lines have to be substituted for the previous
@@ -634,7 +638,8 @@
       Terms <- terms(instl[[i]], data = data)
       m$formula <- Terms
       m <- eval(m, parent.frame())
-      datai <- cbind( datai, model.frame(Terms, m))
+      ## used previously model.frame
+      datai <- cbind( datai, as.data.frame((model.matrix(Terms, m))[,-1]))
     }

     if(i==1) {

Regards,

-Mikko.



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu May 26 02:29:49 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:32:05 EST