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Diffstat (limited to 'docs/mllib-decision-tree.md')
-rw-r--r-- | docs/mllib-decision-tree.md | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/docs/mllib-decision-tree.md b/docs/mllib-decision-tree.md index 0693766990..296277e58b 100644 --- a/docs/mllib-decision-tree.md +++ b/docs/mllib-decision-tree.md @@ -83,19 +83,19 @@ Section 9.2.4 in [Elements of Statistical Machine Learning](http://statweb.stanford.edu/~tibs/ElemStatLearn/) for details). For example, for a binary classification problem with one categorical feature with three categories A, B and C with corresponding proportion of label 1 as 0.2, 0.6 and 0.4, the categorical -features are orded as A followed by C followed B or A, B, C. The two split candidates are A \| C, B +features are ordered as A followed by C followed B or A, B, C. The two split candidates are A \| C, B and A , B \| C where \| denotes the split. ### Stopping rule The recursive tree construction is stopped at a node when one of the two conditions is met: -1. The node depth is equal to the `maxDepth` training parammeter +1. The node depth is equal to the `maxDepth` training parameter 2. No split candidate leads to an information gain at the node. ### Practical limitations -1. The tree implementation stores an Array[Double] of size *O(#features \* #splits \* 2^maxDepth)* +1. The tree implementation stores an `Array[Double]` of size *O(#features \* #splits \* 2^maxDepth)* in memory for aggregating histograms over partitions. The current implementation might not scale to very deep trees since the memory requirement grows exponentially with tree depth. 2. The implemented algorithm reads both sparse and dense data. However, it is not optimized for @@ -178,7 +178,7 @@ val valuesAndPreds = parsedData.map { point => val prediction = model.predict(point.features) (point.label, prediction) } -val MSE = valuesAndPreds.map{ case(v, p) => math.pow((v - p), 2)}.reduce(_ + _)/valuesAndPreds.count +val MSE = valuesAndPreds.map{ case(v, p) => math.pow((v - p), 2)}.mean() println("training Mean Squared Error = " + MSE) {% endhighlight %} </div> |