[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Multiply some colums, discarding others
From: |
Judd Storrs |
Subject: |
Re: Multiply some colums, discarding others |
Date: |
Tue, 24 Nov 2009 14:52:45 -0500 |
On Tue, Nov 24, 2009 at 2:29 PM, Renato S. Yamane
<address@hidden> wrote:
>
> Matrix "B" =
>
> 20.66 A(1,2) * cos(A(1,3))
> 21.47 A(2,2) * cos(A(2,3))
> 22.30 A(3,2) * cos(A(3,3))
> 23.17 A(4,2) * cos(A(4,3))
> 24.07 A(5,2) * cos(A(5,3))
>
You can extract columns using this notation
A(:,1)
A(:,2)
A(:,3)
More about this here:
http://www.gnu.org/software/octave/doc/interpreter/Index-Expressions.html#Index-Expressions
You can then compute the second column at once like this:
A(:,2).*cos(A(:,3))
Notice the .* part. This is element wise multiplication instead of
matrix multiplication. More about this here:
http://www.gnu.org/software/octave/doc/interpreter/Arithmetic-Ops.html#Arithmetic-Ops
You can also combine columns using the [ ] syntax. Putting this all
together, I think this does what you want:
[ A(:,1), A(:,2).*cos(A(:,3)) ]
--judd
- Multiply some colums, discarding others, Renato S. Yamane, 2009/11/24
- Re: Multiply some colums, discarding others, David Bateman, 2009/11/24
- Re: Multiply some colums, discarding others, Norm Hecht, 2009/11/24
- Re: Multiply some colums, discarding others, macy, 2009/11/24
- Re: Multiply some colums, discarding others,
Judd Storrs <=
- Re: Multiply some colums, discarding others, Ron.Simonson, 2009/11/24