# From equation to matrix with for loop

조회 수: 5(최근 30일)
Io7 2021년 9월 18일 15:05
댓글: Image Analyst 2021년 9월 18일 15:46
How can somone change equation into matrix with a for loop? For example if you have something like this:
for i = 1:10
1*x(i) + 2*x(i+1) + 3*x(i+2) = y(i)
end
So, if I were to do this by hand it would be like for i =1
[ 1 2 3 ] * [ x(1) x(2) x(3)]' = y(1)
and for i = 2 you will have
[ 1 2 3 ] * [x(2) x(3) x(4)]' = y(2)
so how can I structure this in a way it gives me a matrix that looks like this:
[ 1 2 3 0; 0 1 2 3] * [x(1) x(2) x(3) x(4)]' = [y(1); y(2)]
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Image Analyst 2021년 9월 18일 15:18
@Bopha NEAK, You can't have the y be on the right side of the equal sign. It must be on the left. See my answer below.

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### 채택된 답변

Image Analyst 2021년 9월 18일 15:16
Do you mean like this:
x = 1 : 12
numRows = 3; % Whatever you want.
y = zeros(numRows, length(x)); % Preallocate.
for row = 1 : numRows
for col = row : length(x) - 2 % Can't have col+2 be longer than x
y(row, col) = 1*x(col) + 2*x(col+1) + 3*x(col+2);
end
end
y
x =
1 2 3 4 5 6 7 8 9 10 11 12
y =
14 20 26 32 38 44 50 56 62 68 0 0
0 20 26 32 38 44 50 56 62 68 0 0
0 0 26 32 38 44 50 56 62 68 0 0
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Image Analyst 2021년 9월 18일 15:46
I really don't know what
1*x(i) + 2*x(i+1) + 3*x(i+2) = y(i)+y(i-1)/2
means. You can't have an assignment like that in MATLAB. Are you trying to do differential equations?

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R2018b

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