The Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.


Math Forum » Discussions » Inactive » comp.soft-sys.math.mathematica

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Working with arrays
Replies: 6   Last Post: Jun 19, 2013 1:20 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
amannuc1

Posts: 29
Registered: 9/18/08
Re: Working with arrays
Posted: Jun 17, 2013 6:17 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On Sunday, June 16, 2013 2:12:22 AM UTC-7, amannucci wrote:
> 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


I appreciate the replies I have received. Yes, CenterDot is the wrong operator! I am a little rusty here. I appreciate the helpful comments.




Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.