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tqchen 2019-04-29 17:50:46 -07:00
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doc/tutorials/model.rst
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@ -72,8 +72,7 @@ Decision Tree Ensembles
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Now that we have introduced the elements of supervised learning, let us get started with real trees. Now that we have introduced the elements of supervised learning, let us get started with real trees.
To begin with, let us first learn about the model choice of XGBoost: **decision tree ensembles**. To begin with, let us first learn about the model choice of XGBoost: **decision tree ensembles**.
The tree ensemble model consists of a set of classification and regression trees (CART). Here's a simple example of a CART The tree ensemble model consists of a set of classification and regression trees (CART). Here's a simple example of a CART that classifies whether someone will like a hypothetical computer game X.
that classifies whether someone will like computer games.
.. image:: https://raw.githubusercontent.com/dmlc/web-data/master/xgboost/model/cart.png .. image:: https://raw.githubusercontent.com/dmlc/web-data/master/xgboost/model/cart.png
:width: 100% :width: 100%
@ -257,7 +256,7 @@ A left to right scan is sufficient to calculate the structure score of all possi
.. note:: Limitation of additive tree learning .. note:: Limitation of additive tree learning
Since it is intractable to enumerate all possible tree structures, we add one split at a time. This approach works well most of the time, but there are some edge cases that fail due to this approach. For those edge cases, training results in a degenerate model because we consider only one feature dimension at a time. See `Can Gradient Boosting Learn Simple Arithmetic? <http://mariofilho.com/can-gradient-boosting-learn-simple-arithmetic/>`_ for an example. Since it is intractable to enumerate all possible tree structures, we add one split at a time. This approach works well most of the time, but there are some edge cases that fail due to this approach. For those edge cases, training results in a degenerate model because we consider only one feature dimension at a time. See `Can Gradient Boosting Learn Simple Arithmetic? <http://mariofilho.com/can-gradient-boosting-learn-simple-arithmetic/>`_ for an example.
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Final words on XGBoost Final words on XGBoost