Color map of the logarithm of the error in density estimation in 2D (left) and 3D (right) as a function of the kernel index and number of neighbors (see Sect. 3 for a complete explanation of this diagram). The dashed line in red is the rough critical limit separating the region susceptible to particle pairing (above the line). The blue dotted line denotes the region where the approach of integrals by summations in density calculation is too sensitive to particle distribution (below the line).