Returns the Integrated Mean Square Error for the unconditional KDE.
Parameters: | bw: array_like :
Returns : —— : CV: float :
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Notes
See p. 27 in [1] For details on how to handle the multivariate estimation with mixed data types see p.6 in [3]
The formula for the cross-validation objective function is:
CV=\frac{1}{n^{2}}\sum_{i=1}^{n}\sum_{j=1}^{N} \bar{K}_{h}(X_{i},X_{j})-\frac{2}{n(n-1)}\sum_{i=1}^{n} \sum_{j=1,j\neq i}^{N}K_{h}(X_{i},X_{j})
Where \bar{K}_{h} is the multivariate product convolution kernel (consult [3] for mixed data types).