How can I index variables inside loops????

Hello all,

How can I simply write a code like this:

function dT=Mesal(T,t)

n=100; dT=zeros(n,1);

for i=1:n

    if i==1
        dT(i)=T(i);
    elseif i==n
        dT(i)=T(i-1);
    else
        dT(i)=T(i+1);
    end
end

Thank you in advance.