Please help with contour issue

I have a data set of x,y,z data that I am trying to create a contour plot from. The data can be displayed in scatter plot just fine, but when i contour plot it, something weird happens in the corner where there were no data points.

Code:

% Create a 100x100 sample mesh grid of the size of the data
[Xgrid, Ygrid]=meshgrid(linspace(min(A(:,1)),max(A(:,1)), 100), linspace(min(A(:,2)),max(A(:,2)), 100));
% Create interpolate class from data
SI=scatteredInterpolant(A(:,1),A(:,2), A(:,3));
% Plot it by grabbing interpolated data from the class at the specific query points
contourf(Xgrid, Ygrid, SI(Xgrid, Ygrid));

Is there a way to stop it from interpolating so strangely in the corner? That whole corner (upper right) should be 1 contour level since there is no data there in the original data set. Instead it looks like a cliff.

Please advise!

Answer 1

[Star Strider]

You’re asking it to extrapolate, and that is never without problems. The scatteredIntrepolant doesn’t offer many extrapolation options, so I can only suggest you experiment with the two (or three) that are available to see what works best for you. The

SI.ExtrapolationMethod = 'none';

option may work best for you.

[Patrick O'Brien]

You are a god among men. That response time was amazing! Here is the new map:

While not giving me exactly what I want (a flat plotted surface in the corner), it at least gets rid of the faulty cliff contours from before. Thank you very much.

[Star Strider]

My pleasure!

If my Answer solved your problem, please Accept it!