Search code examples
javavectormatrixmatrix-multiplicationjama

How can I multiply a matrix by a vector using JAMA?


I'm trying to create a vector from an array of doubles. I then want to multiply this vector by a matrix. Does anyone know how I can achieve this? Below is a really simple example that I would like to get working.

// Create the matrix (using JAMA)
Matrix a = new Matrix( [[1,2,3],[1,2,3],[1,2,3]] );

// Create a vector out of an array
...

// Multiply the vector by the matrix
...

Solution

  • Here is simple example of wanted operation:

    double[][] array = {{1.,2.,3},{1.,2.,3.},{1.,2.,3.}}; 
    Matrix a = new Matrix(array);   
    Matrix b = new Matrix(new double[]{1., 1., 1.}, 1);     
    Matrix c = b.times(a);  
    System.out.println(Arrays.deepToString(c.getArray()));
    

    Result:

    [[3.0, 6.0, 9.0]]
    

    In other words that is:

    enter image description here