This works for any statistics which, when computed across N blocks, are equal
to the weighted mean of the statistics across the N blocks.
est_to_boo(arr, nboot = dim(arr)[3], block_lengths = NULL)3d array with blocked estimates, with blocks in the 3rd dimension.
Number of bootstrap iterations
A 3d array with bootstrap estimates. The first two dimensions are equal to those of arr.
The 3rd dimension is equal to nboot.