Re: ARFF vs CSV

> I am getting different results depending on whether I open the training set as .arff file or .csv file.
>
> Is this normal? Many thanks

Since you didn't post any details, we can only guess...

There are several reasons that I can think of that can influence results:
- different order of labels (ARFF predefines order, CSV could have
order of appearance or alphabetical)
- categorical attribute consisting of numbers is treated as numeric
attribute instead when loaded as CSV
- the ARFF file format limits the number of decimals (by default) to
6, which can lead an attribute with small numbers change its
distribution

These can also affect the class attribute (since it is just another
attribute). And if you use an algorithm that can act as classifier or
regressor, like RandomForest, then switching the class from
categorical to numeric will switch how the algorithm is applied.

Cheers, Peter
-- 
Peter Reutemann
Dept. of Computer Science
University of Waikato, NZ
+64 (7) 858-5174 (office)
+64 (7) 577-5304 (home office)
http://www.cms.waikato.ac.nz/~fracpete/
http://www.data-mining.co.nz/
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