R how to find element index when element is determined from quantile function

How can I find the index of an element, when the element is determined using quantile()? The match() and which() solutions from this similar question do not work (they return NA), and I think they don't work because of rounding issues.

In the case that the quantile result is averaged/interpolated across two indices, can I specify if it takes the lower/higher index? My data x will always be sorted.

Example Dataset (Obviously the 0 and 1 quantiles here are just the min and max, they are just shown for a sanity check)

x <- c(0.000000e+00,9.771228e-09,5.864592e-06,3.474925e-04,9.083242e-04,2.458036e-02)  quantile(x, probs = c(0, 0.5, 1))            0%          50%         100%   0.0000000000 0.0001766785 0.0245803600   

How do I find the indices for these quantiles? Here, the indices are 1,??,6. And I guess the median is the average of two indices, so can I specific that it returns the first or second index?

https://stackoverflow.com/questions/65895317/r-how-to-find-element-index-when-element-is-determined-from-quantile-function January 26, 2021 at 10:58AM