Mediana
M = [25, 25, 25, 25, 25;25,45,35,35,35;25,45,35,35,25;25,45,35,35,25;25,25,25,25,25]
[n,m]=size(M)
for i=2:n-1
for j=2:m-1
M(i,j)=fix((M(i-1,j-1)+M(i-1+j)+M(i-1,j+1)+M(i,j-1)+M(i,j)+M(i,j+1)+M(i+1,j-1)+M(i+1,j)+M(i+1,j+1))/9)
end
end