Expansion on my Devision of matrix by matrix Q?

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Scragmore 2011-10-21

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,

Fangjun Jiang 2011-10-21

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 2011-10-21

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];

Walter Roberson 2011-10-21

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]))

Andrei Bobrov 2011-10-21

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

Scragmore 2011-10-22

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

kron(Qa, y);

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