Summation Equation in matlab code

How can I write this summation equation in matlab ?

N is the number of pixel in the image

Answer 1

[Bhaskar R]

Assuming are vectocrs of the length number of pixels in the image(N)

sigma = (1/N)*sum(C.^2-mu.^2);

[Sajina Rose]

what is the command to obtain pixel count of a 2D image?

[Bhaskar R]

Any image considered as an array in MATLAB i.e number of the array elemets are the number of the pixels in the image.

In your case number of pixels in 2D image is

% using command
N = numel(image);     % this is the command to count of 2D image
% using rows and columns
[rows, columns, dim] = size(image);
N = rows*columns*dim;

[Walter Roberson]

numel() of a grayscale image. size(TheImage,1)*size(TheImage,2) to know the number of pixels for RGB.

The posted code can be simplified by using

mean(C.^2-mu.^2)

Notice that the code is for the vector case, not for the 2D case. N cannot be the number of pixels because you are only using a single subscript.

Answer 2

[Wisal Adnan]

hi please can tell me how make this eq. in matlab

where n start from 2 , m&c constant value