categorical variables

I want to fit an rpart model (regression tree). I transformed 
those variables to factors already and it worked. The problem 
is that when I plot the tree the categorical variables came 
like Emissor=acde, that I suppose it is a code for the numbers 
1,3,4,5. I think I can force R to plot Emissor=1345 or 
something like that

?text.rpart says

  pretty: an integer denoting the extent to which factor levels in
          split labels will be abbreviated.  A value of (0) signifies
          no abbreviation.  A `NULL', the default, signifies using
          elements of letters to represent the different factor levels. 

so the answer is right there on the help page.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595