List of lists elementwise greater/smaller than

Question

I have two lists

a = {{3,1,2},{5,1,3},{4,1,1}}
b = {{4,0,3},{4,2,2},{5,0,2}}

And would like to compare each element within

If{a>b,1,0}

expecting the result

{{0,1,0},{1,0,1},{0,1,0}}

but it doesn't work, how can I get this type of comparison?

you could use 1-UnitStep[b-a]? – kglr May 18 '19 at 19:02 — kglr, May 18 '19 at 19:02
@kglr yep, that achieves the result, thanks – Three Diag May 18 '19 at 19:05 — Three Diag, May 18 '19 at 19:05

score 9 · Accepted Answer · answered May 18 '19 at 19:06

9

Boole@Positive[a-b]

{{0, 1, 0}, {1, 0, 1}, {0, 1, 0}}

1-UnitStep[b-a]

{{0, 1, 0}, {1, 0, 1}, {0, 1, 0}}

answered May 18 '19 at 19:06

kglr

score 3 · Answer 2 · answered May 18 '19 at 19:13

kglr took the fast, vectorized operations. Here are some less optimal ones that you can have a look at for fun or for learning:

Boole@MapThread[Greater, {a, b}, 2]

{{0, 1, 0}, {1, 0, 1}, {0, 1, 0}}

Boole@Apply[Greater, Transpose[{a, b}, {3, 2, 1}], {2}]

{{0, 1, 0}, {1, 0, 1}, {0, 1, 0}}

2 Answers2