What does the function 'norm' do?

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Priya 2014-2-21

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评论： Priya 2014-2-21

采纳的回答： Walter Roberson

Please tell me what does the 2(in bold) in the below expression mean?

residsumsq = norm(y-yhat, 2 )^2;

Also, Is the norm function referring to summation? I read the documentation but it is not clear.

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Answer 1

Walter Roberson 2014-2-21

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在 MATLAB Online 中打开

norm

n = norm(X) returns the 2-norm of input X and is equivalent to norm(X,2). If X is a vector, this is equal to the Euclidean distance. If X is a matrix, this is equal to the largest singular value of X.
The 2-norm is equal to the Euclidean length of the vector.

So it norm(x) is norm(x,2) is sqrt(sum(x.^2))

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Answer 2

Bruno Pop-Stefanov 2014-2-21

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The second input argument of the "norm" function specifies the order of the norm you would like to use. The default norm is the 2-norm, which is the Euclidean distance.

The p-norm is the p-th root of the sum of the terms elevated to the p-th power, i.e.:

http://en.wikipedia.org/wiki/Norm_(mathematics)#p-norm