Computes the additive chi-squared kernel between observations in X and Y
The chi-squared kernel is computed between each pair of rows in X and Y. X and Y have to be non-negative. This kernel is most commonly applied to histograms.
The chi-squared kernel is given by:
k(x, y) = -Sum [(x - y)^2 / (x + y)]
It can be interpreted as a weighted difference per entry.
Read more in the User Guide.
X : array-like of shape (n_samples_X, n_features)
Y : array of shape (n_samples_Y, n_features)
kernel_matrix : array of shape (n_samples_X, n_samples_Y)
As the negative of a distance, this kernel is only conditionally positive definite.
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