n = 10;
shift = 2;
x = (0:n-1) + shift;
y = rand(1,n);
extend = 1e-1;

xx = (-extend:1e-2:n-1+extend) + shift;
yy = cubicspline(xx,x,y);

figure(1); hold on;
plot(x,y,...
  'LineStyle','none' ,...
  'LineWidth', 3     ,...
  'Color',    'red'  ,...
  'Marker',   '+');
plot(xx,yy,...
  'LineStyle', '-'   ,...
  'LineWidth', 3     ,...
  'Color',     'blue',...
  'Marker',    'none');