Write a function called neighbor that takes as input a row vector called v and creates another row vector as output that contains the absolute values of the differences between neighboring elements of v. For example, if v == [1 2 4 7], then the output of the function would be [1 2 3]. Notice that the length of the output vector is one less than that of the input. Check that the input v is indeed a vector and has at least two elements and return an empty array otherwise. You are not allowed to use the diff built-­‐in function.

function v=neighbor(u)
%Input u is a row vector
%Output v is a row vector of length one less than u
%Example: u = [1 2 4 7]
%         v = neighbor(u)
l=length(u);    %number of elements in u
[m,n]=size(u);  %dimensions of u
if m==1         %condition check if u is a row vector
    v=zeros(1,l-1);
    for i=1:l-1
        v(i)=abs(u(i)-u(i+1));   %diff between consecutive elements of u
    end
else
    v=[];
end