linear

clear
clc

x = 0:6;
y = [0 .8415 .9093 .1411 -.7568 -.9589 -.2794];
n = length(x);
xL = linspace(0,6,606);
yI = zeros(1,length(xL));
c = 1;

for i = 1:n-1
    eqn = [ (y(i+1)-y(i))/(x(i+1)-x(i))  (x(i+1)*y(i)-x(i)*y(i+1))/(x(i+1)-x(i)) ];
    for xx = x(i):.01:x(i+1)
        yI(c) = polyval(eqn,xx);
        c=c+1;
    end
end


plot(x,y,'o');
hold on;
plot(xL,yI);
xp=2.5;

grid;