MATLAB: I want to contour plot X,Y coordinate of temperature distribution heat map, the data field is a ring…

colormapcontour

I want to contour plot X,Y coordinate of temperature distribution heat map, the data field is a shape of ring as shown in below
According to Star Strider (https://www.mathworks.com/matlabcentral/answers/526273-creating-2d-contours-from-xyz-values) I have plot something like
But I am tring to get the rid of the inner circle bule color because it suppose to be blank space.
I dont know where went wrong….Can someone help？ please …
code#:
xv = linspace(min(x), max(x), numel(x));
yv = linspace(min(y), max(y), numel(y));
[Xm,Ym] = ndgrid(xv, yv);
Zm = griddata(x, y, t, Xm, Ym);
figure
contourf(Xm, Ym, Zm)
axis([34 54 10 28])

Best Answer

load("data.mat") ; 
% Get center of circles 
C = [mean(x) mean(y)] ; 
% Get radius of inner circle 
dx = C(1)-x ; dy = C(2)-y ; 
Ri = min(sqrt(dx.^2+dy.^2)) ; 
Ro = max(sqrt(dx.^2+dy.^2)) ; 
% Create strip
m = 10 ; n = 100 ; 
R = linspace(Ri,Ro,m) ; 
th = linspace(0,2*pi,n) ; 
[R,T] = meshgrid(R,th) ;
X = C(1)+R.*cos(T) ; 
Y = C(2)+R.*sin(T) ; 
Z = griddata(x,y,t,X,Y) ;
pcolor(X,Y,Z)
shading interp 
colorbar
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