How do I make a column vector to add to my original matrix?

Question

Connor 2023-2-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1906905-how-do-i-make-a-column-vector-to-add-to-my-original-matrix

回答： Voss 2023-2-5

Im trying to solve this: You want to add 4 to each element in the first row of A, subtract 1 from each element in the second row of A, and keep the third row as-is. Create a column vector that you can add to A to perform this task. Call your column vector B.

I have the matrix: A = [1 3 5; -10 -8 -6; (sin(pi/2)) 5^3 (exp(-2))]

I then did:

A = [1 3 5; -10 -8 -6; (sin(pi/2)) 5^3 (exp(-2))]
A = 3×3
    1.0000    3.0000    5.0000
  -10.0000   -8.0000   -6.0000
    1.0000  125.0000    0.1353
B_one = A(1,:) + 4
B_one = 1×3
     5     7     9
B_two = A(2,:) - 1
B_two = 1×3
   -11    -9    -7
B_three = [(sin(pi/2)) 5^3 (exp(-2))]
B_three = 1×3
    1.0000  125.0000    0.1353
B = [B_one B_two B_three]'
B = 9×1
    5.0000
    7.0000
    9.0000
  -11.0000
   -9.0000
   -7.0000
    1.0000
  125.0000
    0.1353

I am trying to make the column vector but my column vector is never the right size and I keep getting the error: Variable B must be of size [3 1]. It is currently of size [9 1]. Check where the variable is assigned a value.

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Answer 1

Torsten 2023-2-5

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移动：Torsten 2023-2-5

What about

B = [4;-1;0]

?

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Answer 2

Voss 2023-2-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1906905-how-do-i-make-a-column-vector-to-add-to-my-original-matrix#answer_1164240

在 MATLAB Online 中打开

A = [1 3 5; -10 -8 -6; (sin(pi/2)) 5^3 (exp(-2))];
B_one = A(1,:) + 4;
B_two = A(2,:) - 1;
B_three = [(sin(pi/2)) 5^3 (exp(-2))];

In constructing B from B_one, B_two, B_three, use vertical concatenation by separating the rows with semicolons, and avoid transposing the result:

B = [B_one; B_two; B_three]
B = 3×3
    5.0000    7.0000    9.0000
  -11.0000   -9.0000   -7.0000
    1.0000  125.0000    0.1353

You can construct a column vector the same way, using vertical concatenation, which can then be added to A. Example:

A = magic(3)
A = 3×3
     8     1     6
     3     5     7
     4     9     2
to_add = [2; 5; -9] % this column vector will be used to add 2 to the first row of A, 5 to the 2nd, -9 to the 3rd
to_add = 3×1
     2
     5
    -9
B = A + to_add
B = 3×3
    10     3     8
     8    10    12
    -5     0    -7