Look at your 'str(mdat)' and you will see that there is not a variable call 'mpg'; it is one of the levels of the 'variable'.
On Mon, Jan 26, 2009 at 11:38 AM, MW Frost <mwfr...@gmail.com> wrote: > Hi everyone. Long time listener, first-time caller here. > > I have a data set that's been melted with the excellent reshape package, but > I can't seem to cast it the way I need to. > > Here's the melted data's structure: > >> str(mdat) > 'data.frame': 6978 obs. of 4 variables: > $ VehType : Factor w/ 2 levels "Car","Truck": 1 1 2 1 1 2 1 1 1 1 ... > $ Year : Factor w/ 6 levels "2003","2004",..: 5 1 5 6 6 2 2 3 2 5 ... > $ variable: Factor w/ 1 level "mpg": 1 1 1 1 1 1 1 1 1 1 ... > $ value : num 22.4 21.5 22.6 22.4 25 ... > > For the purpose of testing, I have stripped out all the variables except for > "mpg." > Casting it without specifying any ids or variables works fine: > >> cast(mdat,,mean) > VehType Year mpg > 1 Car 2003 22.03623 > 2 Car 2004 21.94160 > 3 Car 2005 21.77286 > 4 Car 2006 21.49105 > 5 Car 2007 21.38180 > 6 Car 2008 21.56873 > 7 Truck 2003 16.91461 > 8 Truck 2004 16.88771 > 9 Truck 2005 17.19801 > 10 Truck 2006 17.48225 > 11 Truck 2007 17.40694 > 12 Truck 2008 17.74042 > > I should then be able to make a crosstab of the means by writing a formula, > right? It fails, though: > >> cast(mdat, VehType ~ Year | mpg, mean) > Error: Casting formula contains variables not found in molten data: mpg > > When I make the same table by using "variable" instead of the name of my > variable, it works: > >> cast(mdat, VehType ~ Year | variable, mean) > $mpg > VehType 2003 2004 2005 2006 2007 2008 > 1 Car 22.03623 21.94160 21.77286 21.49105 21.38180 21.56873 > 2 Truck 16.91461 16.88771 17.19801 17.48225 17.40694 17.74042 > > Why can't it find the "mpg" variable when I call it explicitly? > > Thanks, > Matt Frost > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
