Simple subtraction question

Question

I have two lists.

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

I want to subtract a from b and want to get

{{1, 1}, {2, 2}, {3, 3}, {4, 4}}`

When I tried Subtract[a, b], I got an error. How do I fix this?

Basic issue as Artes has shown or duplicate of flexible threading — Kuba, Apr 24 '14 at 05:00
Even better canditate for duplicate Extending listability to coordinates — Kuba, Apr 24 '14 at 05:12

m_goldberg · Accepted Answer · 2014-04-24T05:28:42.720

4

Artes comment as an answer.

a = {{2, 2}, {3, 3}, {4, 4}, {5, 5}};
b = {1, 1};
(# - b)& /@ a

{{1, 1}, {2, 2}, {3, 3}, {4, 4}}

In the special case of your example, because of the way Mathematica defines addition of a scalar to a list, you can do

a - 1

{{1, 1}, {2, 2}, {3, 3}, {4, 4}}

a - x will work for any pair of the form b = {x, x}.

edited Apr 24 '14 at 05:28

answered Apr 24 '14 at 05:09

m_goldberg

Maybe you could add: in this special case the same result can be achieved simply with a - 1. – Jens Apr 24 '14 at 05:10
@Jens. Good idea. Done. – m_goldberg Apr 24 '14 at 05:29

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