How do i write the following mathematical equation in MATLAB

I have written the following mathematical equation in matlab

as

     F = 1/(abs(M)*abs(N))*(sum(sum(abs(SM(i,j)),j,1,abs(N)),i,1,abs(M)));

where F = sigma

I get the following error when i run it.

   Error using sum
   Too many input arguments.
   Error in test_eg2 (line 23)
   F = 1/(abs(N)*abs(G))*(sum(sum(abs(Pop(i,j)),j,1,abs(G)),i,1,abs(N)));

Thanks in advance

Answer 1

[Walter Roberson]

sum() must be given a list of values to total. sum() cannot be passed a variable of summation like you tried to use. sum() is "add these definite and fully pre-computed elements".

You might be tempted to look in the Symbolic Toolbox at symsum() which does accept variables of summation. However, symsum() has the limitation that the variable of summation cannot be used to index a vector or array.

[Christy Jackson]

Will it return an Integer type?

[Christy Jackson]

I tried doing this

    F = 1/(abs(N)*abs(G))*(symsum(symsum((Pop(i,j)),j,0,abs(G)),0,1,abs(N)));

Now i get the following error

    Subscript indices must either be real positive integers or logicals.

and i have taken N = 8 and G = 8

[Walter Roberson]

As I wrote "symsum() has the limitation that the variable of summation cannot be used to index a vector or array"

I am not sure which you are asking about for returning an integer data type. If you are asking about sum() then you can use the 'native' option; see http://www.mathworks.com/help/matlab/ref/sum.html#inputarg_outtype in order for the output to be the same data type as the input.

[Christy Jackson]

I ll try sum() with native option. Thanks

Answer 2

[Thorsten]

If SM is a M * N matrix, you can write

mean2(SM)

or if you don't have the image processing toolbox

mean2(SM(:))

[Christy Jackson]

Will it loop over all the values of M and N

[Thorsten]

Yes.