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EMERGENCY! A mistake or bug? Could you help me?

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Brisk
Brisk 2015-9-29
关闭： MATLAB Answer Bot 2021-8-20
When I use a row vector times a column vector, a unexpected error happens: the reslut be rearranged automatically. For example, the code as
syms x1 x2 x3 real;
X=[x1;x2;x3];
syms u11 u12 u13 real;
U1=[u11;u12;u13];
(X-U1)'*(X-U1)
The answer produced by matlab is
(u11 - x1)^2 + (u12 - x2)^2 + (u13 - x3)^2
But all we know the result should be
(x1 - u11)^2 + (x2 - u12)^2 + (x3 - u13)^2
Why does matlab automatically change the result? What's wrong with the code? Is my mistake or a bug of matlab? Although the two result is equal in this situation, it will change the result of the following code.For example the following code is
syms e11 e12 e13 e21 e22 e23 e31 e32 e33 real
C1=[e11 e12 e13;e21 e22 e23; e31 e32 e33];
(X-U1)'*C1*(X-U1)
Help me, please! Waiting the answer online……
  5 个评论
显示 3更早的评论
Jan
Jan 2015-9-29
Of course Walter's comment is not spam and should be considered carefully. Brisk, did you read it?
When I hit the "This is not spam" button, I get only an error message, but the mark does not disappear. Is this a known bug of the forum?

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WAT
WAT 2015-9-29
编辑：Walter Roberson 2015-9-29
From your post:
The answer produced by matlab is
(u11 - x1)^2 + (u12 - x2)^2 + (u13 - x3)^2
But all we know the result should be
(x1 - u11)^2 + (x2 - u12)^2 + (x3 - u13)^2
Since (a-b)^2 = (b-a)^2 these expressions are equivalent.

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