This will be a quick post - I wanted to share an updated script to export a data frame from R to Weka.  The older version was poorly designed to take in two different data matrices (one for numerical, the other for demographic), and I realized how silly this was in retrospect.  The user would want to hand the function one data frame with everything!  The old link from my previous post will work, however I wanted to clarify a few things:

  • Data is a matrix of size n by m, with m features defining n data objects.
  • Row names and column names are used for data and feature labels, respectively.
  • All variables are assumed to be numeric, with the exception of the row names (the “uid” variable), which is a string.
  • Missing values, currently set as -9999 and NA, are recoded as “?” Change this section (line 28) to fit your data.
  • If you have a nominal outcome variable (eg, you want to color your data by a label in Weka) change the variable type as follows:

@attribute groupVar {1,2}

with {1,2} corresponding to the set of options for the variable (these can also be strings).  You then want to select this variable in the dropdown next to “visualize all”

  • More information on the .arff import format is available here.
  • Edit the script to your liking, it’s pretty simple :O)


I am liking R a lot more than Matlab these days, oh dear!

Suggested Citation:
Sochat, Vanessa. "Export Data from R to Weka." @vsoch (blog), 02 Dec 2013, (accessed 04 Feb 24).