Expansion on my Devision of matrix by matrix Q?

Can I expand on this,

x = [4; 8; 12; 16; 20];

y = [2 4];

Qa = bsxfun(@rdivide,x,y);

Returns Qa = [2 1; 4 2; 6 3; 8 4; 10 5]

Now if I

Qb = Qa*y;

I don't get four columns but an error. Is there a way to step through each column of 'Qa' and multiply by each entry in 'y'.

Additional Q?

I am slowly building up a function with the above math. I have tried creating an output matrix were the series are in a different order.

Function_Matrix_out = [Qa.series1, x, Qa.series2];

again I return and error. Could you explain where I am going wrong.

Thanks,

AD

[Fangjun Jiang]

What do you mean? Why there should be "four columns" when your Qa is 5x2?

What do your mean Qa.series1? You mean the first column? Please use standard term.

[Scragmore]

Sorry don't know what the standard terms are. What I want is each column in QA, to be multiplied respectively by each figure in y, so you would get;

Qb = [4 8 2 4; 8 16 4 8; 12 24 6 12; 16 32 8 16; 20 40 10 20];

Answer 1

[Walter Roberson]

Well, you will have to define the order of the columns you want in the result, but

bsxfun(@times, kron(Qa,[1 1]), kron([1 1],y))

or (different column order)

bsxfun(@times, kron([1 1],Qa), kron(y,[1 1]))

[Scragmore]

Thanks, looks like what I am after for the multiplication of two matrices.

Regarding the column order is there no way to extract specific columns from the answer.

[Walter Roberson]

If you have assigned an array to a variable, say B, then you can extract the N'th column from B by using B(:,N)

If you are trying to do it all as part of one expression (calculate an expression that returns more than one column but extract a single column from it without assigning it to a variable) then see

http://www.mathworks.com/matlabcentral/answers/18892-create-and-indexing-a-matrix-simultaneously

[Scragmore]

Thanks will go and try out.

[Andrei Bobrov]

reshape(bsxfun(@times,reshape(Qa,[],1,2),y),[],4)

[Scragmore]

Thanks again for pointing me in the right direction. I have had a quick play and I think I only need;

kron(Qa, y);