set specific contrasts using lapply

Date: Fri, 11 May 2012 05:38:59 -0700 (PDT)
From: Frank Paetzold<Frank.Paetzold at q-das.de>
To:r-help at r-project.org
Subject: [R] set specific contrasts using lapply
Message-ID:<1336739939629-4626289.post at n4.nabble.com>
Content-Type: text/plain; charset=us-ascii

I have the following data set

 data

    A  B  X1  X2   Y
1 A1 B1 1.1 2.9 1.2
2 A1 B2 1.0 3.2 2.3
3 A2 B1 1.0 3.3 1.6
4 A2 B2 0.5 2.6 3.1

 sapply(data, class)

         A         B        X1        X2         Y
  "factor"  "factor" "numeric" "numeric" "numeric"

I'd like to set a specific type of contrasts to all the categorical factors
(here A and B).
In a loop, this can be done like this:

for (i in 1:length(data))
{
   if (class(data[[i]]) == 'factor')
   {
     contrasts(data[[i]], length(levels(data[[i]])))<-
contr.treatment(levels(data[[i]]), contrast=FALSE);
   }
}

Can i do this without the loop?

I tried to use the function

set.contrasts<- function(x)
{
   if (class(x) == 'factor')
   {
     contrasts(x, length(levels(x)))<- contr.treatment(levels(x),
contrast=FALSE);
   }
}

in

lapply(data, set.contrasts)

However, it doesn't work.

Any ideas?

Thank You