This function is a binned version of 'gsummary'. For each iterator interval
the value of 'bin_expr' is calculated and assigned to the corresponding bin
determined by 'breaks'. The summary statistics of 'expr' are calculated then
separately for each bin.
The bins can be multi-dimensional depending on the number of
'bin_expr'-'breaks' pairs.
The range of bins is determined by 'breaks' argument. For example:
'breaks=c(x1, x2, x3, x4)' represents three different intervals (bins): (x1,
x2], (x2, x3], (x3, x4].
If 'include.lowest' is 'TRUE' the the lowest value will be included in the
first interval, i.e. in [x1, x2].