Hi /r/math,

I know that a Toeplitz matrix is defined such that each diagonal of the matrix is constant. The Toeplitz matrix has some nice properties (it can be multiplied by a vector in O(NlogN), for example).

I've come across a matrix kind of like a Toeplitz matrix, but instead of constant diagonals, each diagonal seems well-approximated by a low-order polynomial. Does this kind of matrix have a name that can help me research it further? To the extent that the information content of the matrix is less than some random matrix, my intuition tells me that it can be multiplied by a vector quickly...perhaps still in O(NlogN). Are there any algorithms for doing that?

Thanks in advance for your help.

(For the curious, I'm an astrophysicist and the matrix is a position-dependent point spread function.)