How to multiply each term in a n*n matrix with elements in a column matrix

Question

ASHA PON 2022-12-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1868383-how-to-multiply-each-term-in-a-n-n-matrix-with-elements-in-a-column-matrix

评论： ASHA PON 2022-12-1

I am having a 14*15 matrix and 15*1 matrix. Now, I need to multiply these two matrix. Thank you in advance.

For example:

A=[ 0.34005, 1.15985, -1.42862; 0.45204, -0.12963, -0.07851; 0.18586, -0.49792, 0.56187; 0.20188, 0.19786, -0.54699]

B=[0; 0; 1; 1]

Expected output:

A11 - First row first column, A21 - Second row first column

C=[A11*B2, A21*B3, A31*B4; A12*B1, A22*B3, A32*B4; A13*B1, A23*B2, A33*B4; A14*B1, A24*B2, A34*B3]

C=[0, 1.15985, -1.42862; 0, -0.12963, -0.07851; 0, 0, 0.56187; 0, 0, -0.54699]

3 个评论
显示 1更早的评论隐藏 1更早的评论

John D'Errico 2022-12-1

在 MATLAB Online 中打开

Confusing. You seem to be mixing up rows and columns, sort of randomly. In your words, you talk about a matrix with 14 rows and 15 columns. But your example has more rows than columns in A. But then the way you then show the indexes for A, it has more columns than rows. Perhaps you don't understand how MATLAB treats arrays.

A = reshape(1:12,4,3)
A = 4×3
     1     5     9
     2     6    10
     3     7    11
     4     8    12

A is a 4x3 matrix. It has 4 rows, and 3 columns. The FIRST index of A is the row number. The second index refers to the column number. So in MATLAB for this matrix, A(1,2) == 5.

ASHA PON 2022-12-1

Thank you for your reply. Actually i have explained my problem in a smaller matrix dimension for better understanding.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

KSSV 2022-12-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1868383-how-to-multiply-each-term-in-a-n-n-matrix-with-elements-in-a-column-matrix#answer_1117258

在 MATLAB Online 中打开

A=[ 0.34005, 1.15985, -1.42862; 0.45204, -0.12963, -0.07851; 0.18586, -0.49792, 0.56187; 0.20188, 0.19786, -0.54699] ;
B=[0; 0; 1; 1] ;
% A11 - First row first column, A21 - Second row first column
% C=[A11*B2, A21*B3, A31*B4; A12*B1, A22*B3, A32*B4; A13*B1, A23*B2, A33*B4; A14*B1, A24*B2, A34*B3]
C=[0, 1.15985, -1.42862; 0, -0.12963, -0.07851; 0, 0, 0.56187; 0, 0, -0.54699] ;
b = zeros(length(B)-1) ; 
for i = 1:length(B)-1
    t = B' ;
    t(i) =[] ; 
    b(i,:) = t ;
end
iwant = A*b