Julia-ism for two-dimensional map?

fortunately, it did not matter… ;-).

below is corrected:

loop1  1.125 ms (79491 allocations: 2.82 MiB)
loop2    84.387 μs (103 allocations: 322.83 KiB)
loop3    14.132 μs (2 allocations: 234.45 KiB)  <-- steveng's loop
loop3  1.089 ms (79491 allocations: 2.82 MiB) <-- steveng's loop, but with .= instead of direct
rv    26.252 ms (215531 allocations: 81.67 MiB)
sa       87.650 μs (20 allocations: 769.02 KiB)  <-- corrected
ra      157.509 μs (85 allocations: 772.58 KiB)
rh    22.710 ms (163682 allocations: 80.42 MiB)