Input formats

Presently, featsel is compatible with two types of input files: the DAT and the XML formats.

The DAT format

This input file format is useful for supervised learning.

Typically, the user has, for a given set S of features, a finite number of samples, each one associating a realization of S with a class label in {1,...,k}. For instance, if the user has seven samples of two features {A, B} defined in {0,1}^2, each sample associated with a label either T or F:

Sample number	A	B	Class label
1	0	1	F
2	1	1	T
3	1	1	T
4	0	1	F
5	1	0	T
6	1	1	F
7	1	0	T

In the above table, A (B) equal to one (zero) means that A (B) is present (absent) in a given sample. The information presented in the table above can be rearranged into a histogram depicting, for each subset of features, the number of occurrences that it was associated to each of the two labels:

A	B		F	T
0	1		1	0
1	0		0	2
1	1		1	2

The featsel DAT format is precisely the table above without the table head:

0 1  1 0
1 0  0 2
1 1  1 2

It is noteworthy to mention that both the feature values and the number of labels do not need to be binary, just non-negative integer; for example, if we have two features, one defined in {0,1} and another one in {0,...,4}, and five labels, one possible DAT file would be:

0 4  1 1 0 0 0
1 3  1 0 2 11 2
1 2  0 0 0 0 3
0 1  2 2 0 7 10