.. _book_fig_chapter9_fig_photoz_tree:


Photometric Redshifts by Decision Trees
---------------------------------------
Figure 9.14

Photometric redshift estimation using decision-tree regression. The data is
described in Section 1.5.5. The training set consists of u, g , r, i, z
magnitudes of 60,000 galaxies from the SDSS spectroscopic sample.
Cross-validation is performed on an additional 6000 galaxies. The left panel
shows training error and cross-validation error as a function of the maximum
depth of the tree. For a number of nodes N > 13, overfitting is evident.



.. image:: ../images/chapter9/fig_photoz_tree_1.png
    :scale: 100
    :align: center


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