NNKCDE is a simple and easily interpretable Conditional Density Estimation (CDE) method. It computes a kernel density estimate of y using the k nearest neighbors of the evaluation point x. The model has only two tuning parameters: the number of nearest neighbors k and the bandwidth h of the smoothing kernel in y-space. Both tuning parameters are chosen in a principled way by minimizing the CDE loss on validation data.
https://ui.adsabs.harvard.edu/abs/2018arXiv180505480I and https://ui.adsabs.harvard.edu/abs/2020A%26C....3000362D