The variance calculation of Random forest regression tree
---------------------------------------------------------
Key: MAHOUT-945
URL: https://issues.apache.org/jira/browse/MAHOUT-945
Project: Mahout
Issue Type: Improvement
Components: Classification
Affects Versions: 0.6
Reporter: Wang Yue
Hi, Mukai
Thanks for your efforts in expand the RF to regression. However, I have a
doubt about your implementation regarding to Regressionsplit.java. The variance
method
"
private static double variance(double[] s, double[] ss, double[] dataSize) {
double var = 0;
for (int i = 0; i < s.length; i++) {
if (dataSize[i] > 0) {
var += ss[i] - ((s[i] * s[i]) / dataSize[i]);
}
}
return var;
}
"
While the variance in my mind should be something like
var += ss[i]/dataSize[i] - ((s[i] * s[i]) / dataSize[i]*dataSize[i]);
Please help correct me if I am wrong. Thanks
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