Function to merge/reduce overlapping ranges

[jorainer]

Definition of the IRanges::reduce function:

       ‘reduce’ first orders the ranges in ‘x’ from left to right, then
       merges the overlapping or adjacent ones.

The reduce function works however only on IRanges (i.e. integer values) while we have real values.

Use case: have m/z ranges (e.g. for chromatographic peaks) and want to get a unique set of non-overlapping ranges. This is some functionality that is also used/needed in e.g. xcms.

Definition:

reduceRanges <- function(x, ...) 

Input: two column matrix, each row being one range and columns being the lower and upper m/z.
Output: two column matrix with the non-overlapping ranges (increasingly ordered by m/z).