When do I need point operator when using power function?

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x y 2013-10-26

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https://ww2.mathworks.cn/matlabcentral/answers/103974-when-do-i-need-point-operator-when-using-power-function

评论： Steven Lord 2022-1-26

采纳的回答： Zack Peters

I want to know ,how can I know when is the point(dot) use in power,when I want to calculate something.

In matrix calculation is always need the . ?

You how to decide use or not use the point

a.^4 a^4

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Answer 1

Zack Peters 2013-10-26

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https://ww2.mathworks.cn/matlabcentral/answers/103974-when-do-i-need-point-operator-when-using-power-function#answer_113299

The '.' syntax is used to denote element-wise multiplication. What this means is that each element of variable 'a' will be raised to the power of 4 rather than have the entire variable 'a' raised to the power of 4.

If 'a' were to be a single value then it doesn't make any difference. However, if 'a' were a matrix then you can begin to see the difference in output of the element-wise operator

~Zack

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Mohammed Hamdalla 2022-1-26

thank you man that really helped.

Steven Lord 2022-1-26

在 MATLAB Online 中打开

As a concrete example:

A = [1 2; 3 4]
A = 2×2
     1     2
     3     4
B = A.*A % Multiply each element of A by itself, element-wise
B = 2×2
     1     4
     9    16
B2 = A.^2 % Same as B
B2 = 2×2
     1     4
     9    16
C = A*A % Perform matrix multiplication
C = 2×2
     7    10
    15    22
C2 = A^2 % Same as C
C2 = 2×2
     7    10
    15    22
% Elements of C are the dot product of the corresponding rows and columns of A
C(1, 2) == dot(A(1, :), A(:, 2)) % true
ans = logical
   1