Splitting function: Approx Equal Splits
splitEqualApprox.Rd
A splitting function takes block ids and block ordering vector (or vectors) and produces a factor that assigns some block ids to one group or another group such that the sum of x within one group is approximately equal to the sum of x in the other group. If x is something like block-size then this equalized the total observations in each split. If x is a covariate, then this splitting approach may make less conceptual sense — if x <- c(1,2,3,4) it would put 1 and 3 in one group and 2 and 4 in another group.