Creating vector and matrix from vector

Question

danielle sisserman 2020-12-10

编辑： James Tursa 2020-12-10

function w = svm(Xtrain, Ytrain)

first, I want to create the following vector:

data = [Xtrain(1)*Ytrain(1) Xtrain(2)*Ytrain(2) ... Xtrain(m)*Ytrain(m)]

Then I want to use vector 'data' to create the following matrix:

A = [data(1) 0 0 ... 0
     data(2) 0 0 ... 0
      .
      .
      .
     data(m) 0 0 ... .]
     
     

How can I easily and efficiantly create the vector data and the matrix A?

Thank you.

Answer 1

James Tursa 2020-12-10

编辑：James Tursa 2020-12-10

Element-wise multiplication is done with the .* operator (with the dot). E.g.,

data = Xtrain .* Ytrain;

The operation data(:) will result in a column vector.

The zeros(rows,columns) will result in a 0's matrix of the requested size.

Then use the square brackets [ ] to concatenate them into a single matrix.

result = [data(:) zeros(rows,columns)];