how i solve these lagranges equations,and generate polynomail

In creating shares following steps are performed. Sir please tell in deatil initialize random coefficients r = round(100*(2*rand(1,k-1)-1)); r(r==0) = 1; generate the polynomial about x with k unknowns P = @(x) (x.^(1:k-1))*r'+s; generate n pieces of partial information i = 1:n d(i,1) = i; d(i,2) = P(i); and obtain k pieces of info x = d(1:k,1)'; y = d(1:k,2)';

 generate Largrange Polynomial
delElement = @(x,i) [x(1:i-1),x(i+1:end)];
lj = @(a,j) prod(delElement(a-x,j)'./delElement(x(j)-x,j)');
Lj = @(y,j) y(j)*lj(0,j);

 reconstruct secret info
s = 0;
 i = 1:k
    s = s+Lj(y,i);