Scilab Program - forward difference formula - IProgramX

Program

function[]=forward(X,Y,x0)
    n=length(X)
    h=X(2)-X(1);
    for i=1:n
        Z(i)=Y(i);
        D(i,1)=Y(i);
    end
    for i=1:n-1
        for j=1:n-i
            d(i,j)=Z(j+1)-Z(j);
            D(i,1)=d(i,j);
        end
        for k=1:n-i
            Z(k)=d(i,k)
            end
    end
    printf('difference table is')
    disp(D)
    y_x=Y(1);
    p=(x0-X(1))/h;
    for i=1:n-1
        pp=1;
        for j=1:i
            pp=pp*(p-(j-1));
         
        end
        y_x=y_x+((pp*d(i,i))/factorial(i))
    end
    printf('value of function at %.4f is %.4f',x0,y_x)
    endfunction
 
Output:

-->X=(100:50:300);

-->Y=[958 917 865 799 712];

-->forward(X,Y,125)
difference table is
  - 87.
  - 21.
  - 7.  
  - 4.  
    712.
value of function at 125.0000 is 939.2500