you can use the inbuilt commands in MATLAB (or) try the formula "plogp". are u using images as input?

Yes images as input .Do you mean by inbuilt commands functions like max()?

I want to know recent methods both research wise and implementation wise too.

Not max. I think you have a command ent

Or you can try this

for i=1 to n

for j=1:n

f= p(i,j) log p(i,j)

end

end