Reduces an array over specified dimensions by applying a function
ArrayReduce[f, array, n]
ArrayReduce[f, array, n1 ;; n2]
ArrayReduce[f, array, {n1, n2, …}]
ArrayReduce[f, array, {{n11, n12, …}, {n21, n22, …}, …}]
array2 = ArrayReduce[Total, array, {2, 4}]//Dimensions
→ {3}