2 added 430 characters in body edited Jul 21 '13 at 11:09 Mr.Wizard♦ 235k3030 gold badges488488 silver badges10901090 bronze badges Also this: {-1, 1}.Mean@list  or this (looks nicer in the front end): Mean[{-1, 1}.list\[Transpose]]  It is worth noting that the first form is considerably more time efficient than the second, though both are fast (warning, several GB RAM used): list = RandomReal[99, {30000000, 2, 2}]; {-1, 1}.Mean@list // Timing // First Mean[{-1, 1}.list\[Transpose]] // Timing // First  0.1902 0.921 The second also uses about 2.5X as much memory as figured by MaxMemoryUsed[]. Also this: {-1, 1}.Mean@list  or this (looks nicer in the front end): Mean[{-1, 1}.list\[Transpose]]  Also this: {-1, 1}.Mean@list  or this (looks nicer in the front end): Mean[{-1, 1}.list\[Transpose]]  It is worth noting that the first form is considerably more time efficient than the second, though both are fast (warning, several GB RAM used): list = RandomReal[99, {30000000, 2, 2}]; {-1, 1}.Mean@list // Timing // First Mean[{-1, 1}.list\[Transpose]] // Timing // First  0.1902 0.921 The second also uses about 2.5X as much memory as figured by MaxMemoryUsed[]. 1 answered Jul 20 '13 at 11:16 Simon Woods 76.5k88 gold badges157157 silver badges295295 bronze badges Also this: {-1, 1}.Mean@list  or this (looks nicer in the front end): Mean[{-1, 1}.list\[Transpose]]