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How do I create a for loop in MATLAB for this?

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Chloe Sim
Chloe Sim on 30 Mar 2020
Commented: Walter Roberson on 29 Apr 2020
Greeting everyone.
I have a these matrix: A is by the order of 10 by 3.
I want to do this calculation: B = (A-min(A))/[max(A)-min(A)]
After that I want B to be by the order of 10 by 3.
Is there a way where I can do a loop of this?

  1 Comment

Walter Roberson
Walter Roberson on 30 Mar 2020
Sure. You can deliberately create a loop or two to find the max and min, and you can deliberately create a loop or two to rescale. You do not need to do those things, but you can.
The trick for the vectorized form is that by default max and min work over only one dimension of a multidimensional array. See the documentation for how to change that to process all dimensions.

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Answers (2)

James Tursa
James Tursa on 30 Mar 2020
Edited: James Tursa on 30 Mar 2020
If you want to use the overall min and max, then just use A(:) for the calculations. E.g.,
B = (A-min(A(:)))/[max(A(:))-min(A(:))];
A(:) is shorhand for reshaping the variable into a column vector.

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Walter Roberson
Walter Roberson on 28 Apr 2020
Are you still required to do a loop for it? (If so, then go ahead and write a loop)
Chloe Sim
Chloe Sim on 29 Apr 2020
Actually, I was guessing using loop will be the best option in the case. But I not sure, how to go about and do it.
Walter Roberson
Walter Roberson on 29 Apr 2020
You can find the per-row min using min(A, [], 2) and you can find the per-row max using similar code. You can do the subtractions . But you should change the division from / to ./
The resulting expression should handle the entire matrix with no loops.

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Steven Lord
Steven Lord on 30 Mar 2020
Use the normalize function with the 'range' method. No for loop is required.

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Walter Roberson
Walter Roberson on 30 Mar 2020
Or use the older, confusingly-named, mat2gray()

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