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let x = [1 2 3;4 5 6] then why norm(x,2) is different from norm(x(:),2)
norm(x,2) = 9.5080 and norm(x(:),2)=9.5394.
I have run this program in Matlab R2012a.
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The two main reasons that your results might not match up each time are uncontrolled conditions and experimental error. Uncontrolled conditions will likely influence your results because you haven't controlled for all of the variables that affect your experiment.
A reason-result relation is a causal relation in which the propositions express an event or state that brings about another event or state. The result occurs regardless of human intention or nonintention. Examples: He was sick, so he stayed home.
Answer: Generally speaking, there is no real difference between the two. In most papers, they are used interchangeably. However, it helps to be consistent throughout the paper.
The results chapter or section simply and objectively reports what you found, without speculating on why you found these results. The discussion interprets the meaning of the results, puts them in context, and explains why they matter.
As defined in Matlab help for norm, the returned value is "The largest singular value" for matrices, and sum(abs(A).^2)^(1/2) for vectors.
Additional reading: wikipedia - matrix norm
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x(:) is a vector, see what Matlab returns if you simply type that at the command-line. x is a matrix. The 2-norm of a matrix and the 2-norm of a vector are calculated in different ways, in general the 2-norm of the vector of the elements of an array will not be the same as the 2-norm of the array. For details see good old Golub and Van Loan.
Why are the 2-norms of matrices and arrays different ? That's maths and therefore off-topic here on SO so I daren't answer.
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