Working with arrays
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- Subject: [mg131190] Working with arrays
- From: amannucci <Anthony.J.Mannucci at jpl.nasa.gov>
- Date: Sun, 16 Jun 2013 05:19:15 -0400 (EDT)
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I thought I understood variables. This sequence completely mystifies me: Clear[lA, xtest] lA = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}; xtest = {4, 5, 6}; lA\[CenterDot]xtest (* First case *) {{a, b}, {c, d}} . {x, y} (* Second case *) The output is: {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}\[CenterDot]{4, 5, 6} {a x + b y, c x + d y} How do I force matrix multiplication to actually occur, as in the second answer? Why does Mathematica do the matrix multiply in the second case but not the first? Thanks for any help. -Tony
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