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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?

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

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

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