Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Introducing LETOR 4.0 Datasets   LETOR is a package of benchmark data sets for research on LEarning TO Rank,
which contains standard features, relevance judgments, data partitioning,
evaluation tools, and several baselines. Version 1.0 was released in April
2007. Version 2.0 was released in Dec. 2007. Version 3.0 was released in Dec.
2008. This version, 4.0, was released in July 2009. Very different from
previous versions (V3.0 is an update based on V2.0 and V2.0 is an update based
on V1.0), LETOR4.0 is a totally new release. It uses the Gov2 web page
collection (~25M pages) and two query sets from Million Query track of TREC
2007 and TREC 2008. We call the two query sets MQ2007 and MQ2008 for short.
There are about 1700 queries in MQ2007 with labeled documents and about 800
queries in MQ2008 with labeled documents. If you have any questions or
suggestions about the datasets, please kindly email us (letor@microsoft.com).
Our goal is to make the dataset reliable and useful for the community.

13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph