How to interpolate the data inside the polygon?

I have the data in the vertical column( A,B,C,D,E,F,G,H) and the solid dot in each column represents the data location.

I want to interpolate the data inside the polygon(KLMNOPQRSTU) only ,as given in the attached figure.

[Jiri Hajek]

Hi, please try to clarify. From the figure it seems you could just intepolate the data A-h and subtract the value below K-L line...

[TAPAS]

Ignore the things below K-L line.

[Mathieu NOE]

data ? code ?

[TAPAS]

I have attached the excel file ,from given x,y,z I want to interpolate data inside the polygon.The polygon here is just covering all the data points and i want to interpolate only inside the polygon.

[KSSV]

Read about interp2, scatteredInterpolant

[TAPAS]

I tried but getting an absurd figure

Answer 1

[KSSV]

T = readtable('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1222307/Book2.xlsx') ;
x = T.X ;
y = T.Y ;
z = T.Z ;

[X,Y] = meshgrid(min(x):90:max(x),min(y):1:max(y)) ;
Z = griddata(x,y,z,X,Y) ;

pcolor(X,Y,Z)

h = pcolor(X,Y,Z) ; 
h.EdgeColor = 'none'  ;