检查给定点（x，y）是否低于或高于曲线

Question

I have a task to solve using Matlab. I have two curves generated with 'fit' functions in matlab. their equations are as follows:

fo =

 Linear model Poly2:
   fo(x) = p1*x^2 + p2*x + p3
 Coefficients (with 95% confidence bounds):
   p1 =   -0.005234  (-0.007191, -0.003278)
   p2 =      0.8276  (0.537, 1.118)
   p3 =       39.62  (30.59, 48.65)

fu =

 Linear model Poly2:
   fu(x) = p1*x^2 + p2*x + p3
 Coefficients (with 95% confidence bounds):
   p1 =   -0.004092  (-0.01098, 0.002796)
   p2 =       0.856  (-0.1671, 1.879)
   p3 =       14.73  (-17.06, 46.53)

My task is to check if any given point (x,y) is either below the curve fu or above the curve fo. (ideally the point(x,y) should be between these curves for the next process to begin.)

How do i approach??

Answer 1

something like

% your data
xm=1;
ym=5;

if ym<fu(xm) & ym>fo(xm)
   % good!
else
  % bad :(
end

?

Answer 2

For any given equation, any order , Say

Y= a1x2 + b1x + c1, You can write, Y-(a1x2 +b1x +c1) = 0 Let this be y - f(x) = 0

And let your point be (x',y') If y' - f(x') > 0, your point lies outside the curve and if this is < 0 it is inside.

Hope this helps.