Need help understanding rescale()

Question

Adrian Velasquez 2022-8-1

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https://ww2.mathworks.cn/matlabcentral/answers/1772235-need-help-understanding-rescale

评论： Adrian Velasquez 2022-8-2

I have an array x that I'm running rescale on. However, I'm not understanding the output that I'm getting. Should it not be [1.000 0.9000 0.9500 0.9500; 0.7000, ect] I'm not sure if it's a problem with my code or my understanding of how rescale() works. Any tips help. Thank!

function X = rescale_scores()
    x = [100  90  95  95;  70  50  60   60; 80  70  90  80]
    [m,n] = size(x);
 
    A = rescale(x)
end
% OUTPUT THAT I'M GETTING
x =
   100    90    95    95
    70    50    60    60
    80    70    90    80
A =
    1.0000    0.8000    0.9000    0.9000
    0.4000         0    0.2000    0.2000
    0.6000    0.4000    0.8000    0.6000

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Answer 1

Jeffrey Clark 2022-8-1

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https://ww2.mathworks.cn/matlabcentral/answers/1772235-need-help-understanding-rescale#answer_1019425

@Adrian Velasquez, according to rescale documentation each element should be rescaled to [0..1] using this method:

l + [(A-inmin)./(inmax-inmin)].*(u-l)

to scale the elements of an array A when the values of A are within the bounds of inmin and inmax.

If l and u are not specified, then rescale uses the default values 0 and 1, respectively.
If the 'InputMin' name-value pair is not specified, then rescale sets its value to the default min(A(:)).
If the 'InputMax' name-value pair is not specified, then rescale sets its value to the default max(A(:)).

In your case since l = 0, u = 1, InputMin = min(x(:)) and InputMax = max(x(:) it becomes:

0+[(x-50)./(100-50)].*(1-0) == (x-50)/50 ==> 100 becomes 1, 50 becomes 0 and so on.

So rescale works as advertised.

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Adrian Velasquez 2022-8-2

Yes that makes sense! I didn't realize that the minimum defaulted to the minimum of the input if it is not explicitely specified. Thanks for the help!

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