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.
- Xarray-like of shape (n_samples_X, n_features)
- Yndarray of shape (n_samples_Y, n_features), default=None
- kernel_matrixndarray of shape (n_samples_X, n_samples_Y)
As the negative of a distance, this kernel is only conditionally positive definite.
Zhang, J. and Marszalek, M. and Lazebnik, S. and Schmid, C. Local features and kernels for classification of texture and object categories: A comprehensive study International Journal of Computer Vision 2007 https://research.microsoft.com/en-us/um/people/manik/projects/trade-off/papers/ZhangIJCV06.pdf