MATLAB: How plot a correct interpolation with surf plot

Question

Im using the code:

load A_PRE.mat; %find it attached

load Aelec.mat; %find it attached
figure(1)
X=A_PRE(:,1);  Y=A_PRE(:,4); Z=A_PRE(:,5);
[xq,yq]=meshgrid(linspace(min(X),max(X),100),linspace(min(Y),max(Y),100));
zq=griddata(X,Y,Z,xq(:),yq(:),'linear');
[c,h]=contourf(xq,yq,reshape(zq,100,100),'LineStyle','none','LevelStep',100); 
hold on
plot(cotas(:,1),cotas(:,2),'k','linewidth',4) %elevation data
hold on
scatter(X,Y,'filled','k')
figure(2)
plot3(Aelec(:,2),Aelec(:,3),Aelec(:,4),'k','linewidth',2);
hold on
scatter3(A_PRE(:,2),A_PRE(:,3),A_PRE(:,4),'filled','k')
hold on
level=A_PRE;
x = level(:,2);  y = level(:,3); z = level(:,4); c = level(:,5);
yv = linspace(min(level(:,3)), max(level(:,3)), 100); 
zv = linspace(min(level(:,4)), max(level(:,4)), 100);
[Y,Z] = meshgrid(yv, zv);
X = griddata(y,z,x,Y,Z,'cubic'); 
C = griddata(y,z,c,Y,Z,'cubic');
yA = Aelec(:,3); zA = Aelec(:,4);
in = inpolygon(Y,Z,yA(1:end-1),zA(1:end-1));
Z(in) = nan;
surf(X, Y, Z, 'cdata',C);
shading interp

for plotting the contour:

using surf function and using X and Y coordinates for its location, but when a use the same view of the 2D contour it seems to be interpolated wrong, any ideas about what could be my mistake? how could a I get a contour plot for figure 2 as similar than figure 1.

As you see, the yellow values seems to be affected with the other data using surf plot, any idea about how to obtain the interpolation plot as similar as fig 1? Thanks in advance

Answer 1

It happens because of different scales of data. Don't know why MATLAB get confused about it (even linear interpolation)

scale and center your data before interpolation

sc = (max(z)-min(z))/(max(y)-min(y));
y = y - mean(y);
x = x - mean(x);
y = y*sc;
x = x*sc;
yv = linspace(min(y), max(y), 50); 
zv = linspace(min(z), max(z), 50);
[Y,Z] = meshgrid(yv, zv);
X = griddata(y,z,x,Y,Z,'cubic'); 
C = griddata(y,z,c,Y,Z,'cubic');