how n(20*20 matrix) can obtain

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vipul utsav 2012-12-28

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     mean(s./n)=0.5
                 s=  1  2  3  4  5 ...20
                     20 19 18 17 16....1
                     1  2  3  4  5 ...20
                     20 19 18 17 16....1
                     1  2  3  4  5 ...20
                     20 19 18 17 16....1 
                     ...................   
                     ...................
                     20 19 18 17 16....1

s is a 20*20 matrix and it is fix; how n(20*20 matrix) can obtain such it follow above equation.

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Image Analyst 2012-12-28

You're posting enough now that you should learn how to highlight your code and click the {}Code button to format your code. Make sure there is a blank line before the first line of code though.

Image Analyst 2012-12-28

You don't click {}Code first. If you do that, you get that useless "if true" like you just did. Just do what I said: make sure there's a blank line before your code, then highlight all your code (even intermediate blank lines if it's a long bit of code), then click {}Code.

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Answer 1

Image Analyst 2012-12-28

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在 MATLAB Online 中打开

It's trivial. Just solve the equation for n! You'll find it's twice s. Here's proof:

% Construct s.
s2rows = [1:20;20:-1:1];
s = repmat(s2rows, [10,1])
% Here's n.  It's just twice s!
n = s /0.5
% Proof that the mean = 0.5
theMean = mean2(s ./ n)

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Image Analyst 2012-12-28

And it doesn't matter WHAT s is. It could be anything at all. Just look at the equation - it's really basic math. No matter what s is, s over (2s) will be 1/2 for every single element, and thus give you a mean of 0.5. Is there something either I or you are not understanding here?

vipul utsav 2012-12-29