将八度功能转换为Java

Question

I'm trying to convert some Octave functions to Java, but I'm not sure I'm this right.

function [y,a] = forwardProp(x, Thetas)
    a{1} = x;
    L = length(Thetas)+1;
        for i = 2:L,
            a{i-1} =[1; a{i-1}];
            z{i} =Thetas{i-1}*a{i-1};
            a{i} =sigmoid(z{i});
        end 
    y = a{L};
end

My Java Function

public class ForwardProp {

public static DoubleMatrix ForwardProp(DoubleMatrix x, DoubleMatrix Thetas) 
{
    DoubleMatrix a = new DoubleMatrix();
    a = DoubleMatrix.concatHorizontally(DoubleMatrix.ones(a.rows, 1), x);

    int L = Thetas.length + 1;

    DoubleMatrix z = new DoubleMatrix();

    for (int i = 2; i <= L; i++) 
    {
        a.put(i - 1, a.get(i - 1));
        z.put(i, (Thetas.get(-1) * a.get(i - 1)));
        a.put(i, Sigmoid(z.get(i)));
    }
    return a;
    }
}

Can someone tell me if this is right???

Answer 1

As far as I can tell, you are committing a double-fencepost error here:

int L = Thetas.length + 1;

L now equals 1 more than the number of elements in the matrix...

for (int i = 2; i <= L; i++) ...and you are now looping with Thetas.get(i - 1) all the way up to an index that is 2 greater than the highest index available from Thetas.get(int) .

Remember, Thetas.get(int) directly accesses the internal array that stores this matrix's data. This can only accept indices from 0 to Thetas.length - 1 . So when you call Thetas.get(-1) you will always get an error because -1 is not a valid array index; when you get to the end of the loop and call Thetas.get(i - 1) , you will get an error again because there is no element at that location.

You are also initializing your output matrix with DoubleMatrix z = new DoubleMatrix(); , which returns a 0x0 empty matrix with no elements. That's not what you want either.

Try to make sure you know which indices your data is in, then rewrite it when you know how to reference the data you are using.