Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pattern Recognition Approaches to Solving Combinatorial Problems in Free
  Groups   We review some basic methodologies from pattern recognition that can be
applied to helping solve combinatorial problems in free group theory. We
illustrate how this works with recognizing Whitehead minimal words in free
groups of rank 2. The methodologies reviewed include how to form feature
vectors, principal components, distance classifers, linear classifiers,
regression classifiers, Fisher linear discriminant, support vector machines,
quantizing, classification trees, and clustering techniques.

29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
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The categories of this paper are: eess
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc