sparse arff parser

[busarobi@…]

The ArffParser should be able to read the official sparse arff format. This is importnat for release.

[anonymous]

It's ready. There is some questions what we should decide together:

1) the arff parser assumes that the class feature is called 'class' whereas the weka considers the last feature as label feature.
2) we do not allow spaces in the name of labels whereas the weka allows this but in this case the name of labels should be put between

example: 'lo fasz' can be the name of a label but only lo fasz cannot be since it counts as two labels

3) if the data is in sparse format, we do not allow now to use sparse label representation just like the weka, however we could do this.

{0 1,3 5.4,7 8.0,9 {alma 1.0 korte -2.0}}