n = 10; %the sample size
x1 = linspace(0,5,n); %this is to simulate your x1
y1 = rand(1,n); %this is to simulate your y1
p = polyfit(x1,y1,n)
x2 = linspace(0,5,10000); %this is to simulate x2, that should be the domain of the interpolating function
y2 = polyval(p,x2)
scatter(x1,y1)
hold on;
plot(x2,y2)
