如何将给定矩阵每一行中的所有元素与给定向量的相应元素相乘，然后在MATLAB中求和？

Question

例如，给定矩阵randn(3,2) -3行，2列和乘数randn(1,2)) 2列的向量，我想获得一个大小为(3, 1)的向量，其中每行将代表矩阵的行元素与给定的乘法器的每个元素相乘的总和

row_element_1*mul_element_1 + row_element_2*mul_element_2

Answer 1

Sounds like you want a matrix-vector multiplication.

1> x = randn(3, 2)
x =

   0.62055  -1.08060
  -0.24064  -2.56097
  -0.53202  -0.49712

2> y = randn(1, 2)
y =

  -1.26010  -0.25200

3> x * y'
ans =

  -0.50964
   0.94860
   0.79567

Note the transposition y' .

Answer 2

I think you can do this with a combination of bsxfun and sum, like so:

a = rand(3,2);
b = rand(1,2);
result = sum(bsxfun(@times,a,b),2)

result =

   0.333379034494579
   0.613480382112731
   0.093702948350719

Note dimension argument to SUM to sum along each row (rather than the default, which is down columns). BSXFUN applies a binary function with scalar expansion, which is ideal for the multiplication part here.

Answer 3

A = randn(3, 2);
B = randn(1, 2);

C = A(:, 1) * B(1) + A(:, 2) * B(2);   % size(C) = [3, 1]

If you have to scale to a much larger array with lots more columns and didn't want to write out the equation for C in full, you can use repmat and element-wise multiplication

A = randn(300, 200);
B = randn(1, 200);

C = sum(A .* repmat(B, 300, 1), 2);