Implementation.: The function is based on a weighted version of the quickselect/Find algorithm with the Bentley and McIlroy (1993) 3-way partitioning scheme. For very small arrays, we use insertion sort.
Compatibility.: For equal weighting, i.e., when all elements in w are equal, weighted_quantile is identical with type = 2 of stats::quantile; see also Hyndman and Fan (1996).
Returns
Weighted estimate of the population quantiles
References
Bentley, J. L. and McIlroy, D. M. (1993). Engineering a Sort Function, Software - Practice and Experience 23 , 1249--1265. tools:::Rd_expr_doi("10.1002/spe.4380231105")
Hyndman, R.J. and Fan, Y. (1996). Sample Quantiles in Statistical Packages, The American Statistician 50 , 361--365. tools:::Rd_expr_doi("10.1080/00031305.1996.10473566")