trying to write matlab code for Frobenius norm of an mxn matrix

Hello, hoping someone can guide me, i asked my question on another forum, but realised this place could have better help,....with matlab, I have provided the link below, cause I cannot write the mathematical formula on here,

http://www.physicsforums.com/showthread.php?t=673897

any help greatly appreciated.

the code i have written so far is

function w = frobeniusnorm(a,m,n) for i =1:m sm = 0 for j =1:n sm = sm+A(i,j)*a^2(i,j); end

which does not work

[Muthu Annamalai]

The problem with your code, Shelly, seems to be

function w = frobeniusnorm(a,m,n)
  for i =1:m
    sm = 0
    for j =1:n
      sm = sm+A(i,j)*a^2(i,j);
    end
  end
end

you have sm = 0, reinitialized every time. You need to move it out of the first for-loop.

A better solution without using the built-in norm() function is to write out sums,

sm =  sqrt( sum(sum(A.^2)) )

I would strongly recommend you read the MATLAB tutorial on matrix indexing http://www.mathworks.com/help/matlab/math/matrix-indexing.html and use what is called 'vectorized code'

[SARATHKUMAR]

i need to find the Pulsatile velocity profile using frobenius method if any one have code for that please send on this question comment

Answer 1

[Wayne King]

Why not just use:

 norm(X,'fro')

For example:

 X = randn(8,8);
 norm(X,'fro')

Answer 2

[shelly]

yeah I know this particular function,n but I have to first write the code and than compare my answers with matlab's built in function.

Answer 3

[Rolando Molina]

I think that this code was the original intention, and works:

function fn = frobenius_norm_mn_matrix(A,m,n) si=0; for i =1:m sj = 0; for j =1:n sj = sj+A(i,j)^2; end si=si+sj; end fn=sqrt(si) end