Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A New Strategy for Estimating Photometric Redshifts of Quasars   Based on the SDSS and SDSS-WISE quasar datasets, we put forward two schemes
to estimate the photometric redshifts of quasars. Our schemes are based on the
idea that the samples are firstly classified into subsamples by a classifier
and then photometric redshift estimation of different subsamples is performed
by a regressor. Random Forest is adopted as the core algorithm of the
classifiers, while Random Forest and kNN are applied as the key algorithms of
regressors. The samples are divided into two subsamples and four subsamples
depending on the redshift distribution. The performance based on different
samples, different algorithms and different schemes are compared. The
experimental results indicate that the accuracy of photometric redshift
estimation for the two schemes generally improve to some extent compared to the
original scheme in terms of the percents in \frac{|\Delta z|}{1+z_{i}}<0.1 and
\frac{|\Delta z|}{1+z_{i}}<0.2 and mean absolute error. Only given the running
speed, kNN shows its superiority to Random Forest. The performance of Random
Forest is a little better than or comparable to that of kNN with the two
datasets. The accuracy based on the SDSS-WISE sample outperforms that based on
the SDSS sample no matter by kNN or by Random Forest. More information from
more bands is considered and helpful to improve the accuracy of photometric
redshift estimation. Evidently it can be found that our strategy to estimate
photometric redshift is applicable and may be applied to other datasets or
other kinds of objects. Only talking about the percent in \frac{|\Delta
z|}{1+z_{i}}<0.3, there is still large room for further improvement in the
photometric redshift estimation.

23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat