Combine several CTest results by multiplying their densities

Reproduces the combination step of mmc8 (reconstruct_parameters_Devonian.R), using a base-R weighted quantile instead of Hmisc::wtd.quantile.

Usage

ctest_combine(results, what = "k", n = 1000)

results: CTest results to combine (list, ideally named): each element is a ctest object from ctest or a numeric vector of samples (e.g. precession constants in years). The kernel densities of all elements are multiplied. Required, no default.
what: Column of the samples data frame of the ctest objects that is combined (character), e.g. "k" (precession constant, yr), "SR" (sedimentation rate, m/kyr), "obl_ks3" or "g2"; ignored for numeric vectors. Default="k".
n: Number of points of the grid on which the densities are evaluated and multiplied (integer, > 1). Default=1000.

list: grid `x`, combined density, mean (median of the combined density) and sd (half the inter-quartile span, as in the paper)