A question about product operation

Hello all!

I'm not sure if this was explained before, but I could not find any answer to this.

So, if i have x=[a b c] and y=[d e f] I'd like to know (if it's possible) how I could obtain:

 .
z=
   h i j 
   k l m 
   n o p                     
where:
h=a*d    k=a*e    n=a*f
i=b*d    l=b*e    o=b*f
j=c*d    m=c*e    p=c*f

Thanks!

Answer 1

[Jan]

x = [1, 2, 3]
y = [10, 20, 30]
z = x' * y

The matrix multiplication of a column vector with a row vector replies the dyadic product. x*y' would reply the dot-product.

Slower alternative:

z = bsxfun(@times, x', y)

[Dan P]

Thank you!

[Simon]

Beaten by 1 minute ... ;-)

[Dan P]

Could you tell me how i could implement this in Simulink?

I put two constant blocks (one with x and one with y) and i put a product block. At the output of X, before connecting to the first input of the product i have to put a transpose block. I've tried "Transpose" and "Reshape" blocks but they didn't do the job. (the result it's not a 3x3 matrix) I also tried to use the blocks from the "User-defined functions" but I did not succeed.

Yes, if i make a .m file or simply type in command line z=x'*y it works (i have a 3x3 vector in workspace called z).

Any idea how this can be done in Simulink?

[Jan]

As described in the documentation, you can set the product block to "Matrix Mode". I've never worked with Simulink, but Google showed me this information after a few seconds of searching. Does it help already?

[Sean de Wolski]

Of course you could also put this inside of a MATLAB function block.

[Jan]

Dan p wrote:

 I also tried to use the blocks from the "User-defined functions" but I did not succeed.

Please show us, what you have tried and explain "did not succeed" with details.

Answer 2

[Simon]

Hi!

x = [1, 2, 3]; % row vector
y = [2; 3; 4]; % column vector

z = y * x;