zsort

     plot FOO using x:y:z:color zsort with points lc palette

Input data is sorted immediately after input, prior to applying any smoothing options. Note that some smoothing options will re-sort the data, in which case zsort has no effect on the plot. If z is not auto-scaled, points with z value out of range are flagged but not deleted.

The intended use is to filter presentation of 2D scatter plots with a huge number of points so that the distribution of high-scoring points remains evident. Sorting the points on z guarantees that points with a high z-value will not be obscured by points with lower z-values.