scikit-learn/scikit-learn — comment on commit 7ba791d16859aa68045913d0529add74a9eae71f
File: doc/modules/tree.rst line 206
By ogrisel:

I don't understand why it is stated that masking avoids a copy of data. If masking is "using boolean mask", then this is not the case:

```
In [3]: a = np.random.randn(1e8)

In [4]: b = a[a > 0]

In [5]: b.flags.owndata
Out[5]: True
```

And by looking at top, I can tell you that the memory is allocated for both a and b in my python process.