Matrix Multiplication column and vector

Hi,

I am trying to solve this problem:

A is 1 column of 100k results; B is a vector of 10 weights; I need a matrix of 10 columns and 100k rows:

[(result line 1)*W1 (result line 1)*W2 (result line 2)*W1 (result line 2)*W2 ...

Thank you very much,

[Torsten]

I don't understand the logic behind

[(result line 1)*W1 (result line 1)*W2 (result line 2)*W1 (result line 2)*W2 ...

Could you explain ?

Best wishes

Torsten.

Answer 1

[Andrei Bobrov]

A is 1 column of 100k results; W is a vector of 10 weights;

A(:)*W(:).'

[Alexandra]

Thanks, it worked! Could you help me on just one more operation?

So now I have a 100k*10 matrix. I also have a 10*1 matrix of target values for each weighted result.

So, i am trying to evaluate how many values in the first column of 100k*10 are bellow the first value in the vector, and by how much. Next, how many values in the second column are bellow the second number and by how much. Therefore I am trying to get a 10*1 vector of number of cases bellow target for each target and a 100k*10 matrix of the difference to target. I written this: A = zeros(size(100k*10 matrix)); n = numel(A); for k=1:n if 100k*10 matrix < OBJECTIVO A = OBJECTIVO - 100k*10 matrix; else A = 0; end end PA = (n - sum(A == 0))/n; But get the same error Error using < Matrix dimensions must agree.

Thanks a lot

Answer 2

[Lukas Bystricky]

Try

    B*A

where A is a row vector and B is a column vector (you may need to transpose them to get them in this form). That will give a matrix with length(B) rows and length(A) columns.

[Alexandra]

I tried: Error using * Inner matrix dimensions must agree.

[Lukas Bystricky]

The first vector has to be a column vector and the second a row vector, otherwise the multiplication isn't defined. You can turn a row vector into a column vector (or vice versa) by using

 A = A'

for example.