Matrix manipulation

2011 3 25
4 个回答
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Hi I'm new to Matlab and seem to be struggling again. I'm trying to subtract corresponding elements from two image matrices i.e.
matrix 1= A B matrix 2= a b C D c d
I'm trying to get (A-a)^2+(B-b)^2.....
Thanks in advance for any help, it;s really appreciated.

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回答（4 个）

the cyclist
the cyclist 2011-3-25

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Not 100% if this is what you mean, but ...
M1 = [1 2 3 4];
M2 = [5 6 7 8];
M3 = (M1-M2).^2;

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Karen Rafferty
Karen Rafferty 2011-3-25
Yeah that seems like it. I'm trying to do it for two 568 by 752 matrices. From the above I'd be doing M3=(1-5)^2 + (2-6)^2 + (3-7)^2+ (4-8)^2
Is it possible to do so? I'm guessing I'd need a for loop.
Thanks
Matt Fig
Matt Fig 2011-3-25
No FOR loop is needed.
M3 = sum((M1-M2).^2)
If you expect a scalar from the operation, do this:
M3 = sum((M1(:)-M2(:)).^2)
Karen Rafferty
Karen Rafferty 2011-3-25
I tried this: M3 = sum((Groundtruth-Haarbk2).^2)
but got the error message:
??? Error using ==> minus
Class of operand is not supported.
Matt Fig
Matt Fig 2011-3-25
Yes, what version are you using, because this works find on my system.
Try this:
sum((Groundtruth-double(Haarbk2)).^2)
Karen Rafferty
Karen Rafferty 2011-3-25
Thanks that seems to be working now

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Sean de Wolski
Sean de Wolski 2011-3-25

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M3 = sum((Groundtruth(:)-double(Haarbk2(:))).^2);
Karen Rafferty
Karen Rafferty 2011-3-25

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I've tried to implement these by: for i = 1:M for j = 1:N Ans= sum(abs(Groundtruth(i,:)-Haarbk2(i,:))).^2; end end
But I keep getting the error message:
??? Error using ==> minus Class of operand is not supported.

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Matt Fig
Matt Fig 2011-3-25
So what does this return:
class(Groundtruth)
class(Haarbk2)
Karen Rafferty
Karen Rafferty 2011-3-25
They give:
>> class(Groundtruth)
ans =double
>> class(Haarbk2)
ans =uint8
Should they be the same?
Sean de Wolski
Sean de Wolski 2011-3-25
Yes. You can't have a negative unsigned integer.
Haarbk2 = double(Haarbk2);

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Karen Rafferty
Karen Rafferty 2011-3-25

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Thank you soo much for all your help, I think I've it sorted now :D

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