gabor.jl

"""
    gaborkernel(;
        sqexponential_transform=IdentityTransform(), cosine_tranform=IdentityTransform()
    )

Construct a Gabor kernel with transformations `sqexponential_transform` and
`cosine_transform` of the inputs of the underlying squared exponential and cosine kernel,
respectively.

# Definition

For inputs ``x, x' \\in \\mathbb{R}^d``, the Gabor kernel with transformations ``f``
and ``g`` of the inputs to the squared exponential and cosine kernel, respectively,
is defined as
```math
k(x, x'; f, g) = \\exp\\bigg(- \\frac{\\| f(x) - f(x')\\|_2^2}{2}\\bigg)
                 \\cos\\big(\\pi \\|g(x) - g(x')\\|_2 \\big).
```
"""
function gaborkernel(;
    sqexponential_transform=IdentityTransform(), cosine_transform=IdentityTransform()
)
    return (SqExponentialKernel() ∘ sqexponential_transform) *
           (CosineKernel() ∘ cosine_transform)
end