function quadterp,x0,y0,x1,y1,x2,y2,x
  P0=(X-X1)*(X-X2)/((X0-X1)*(X0-X2))*Y0;
  P1=(X-X0)*(X-X2)/((X1-X0)*(X1-X2))*Y1;
  P2=(X-X0)*(X-X1)/((X2-X0)*(X2-X1))*Y2;
  return,(P0+P1+P2)
end