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

6 views (last 30 days)
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.

Accepted Answer

Torsten
Torsten on 5 Feb 2023
Moved: Torsten on 5 Feb 2023
What about
B = [4;-1;0]
?

More Answers (1)

Voss
Voss on 5 Feb 2023
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

Categories

Find more on Multidimensional Arrays in Help Center and File Exchange

Products


Release

R2022b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!