# Simple subtraction question [duplicate]

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?

• If you don't know start with Map, i.e. # - b & /@ a. – Artes Apr 24 '14 at 4:26
• Basic issue as Artes has shown or duplicate of flexible threading – Kuba Apr 24 '14 at 5:00
• Even better canditate for duplicate Extending listability to coordinates – Kuba Apr 24 '14 at 5:12

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}.

• Maybe you could add: in this special case the same result can be achieved simply with a - 1`. – Jens Apr 24 '14 at 5:10
• @Jens. Good idea. Done. – m_goldberg Apr 24 '14 at 5:29