Griddata is omitting boundary data

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Abhijeet Marekar 2018-11-21

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https://ww2.mathworks.cn/matlabcentral/answers/431118-griddata-is-omitting-boundary-data

评论： Abhijeet Marekar 2018-11-21

Griddata.JPG

I am trying to plot 3d mesh plot using grid data. I have imported x,y, z cordinate data from .txt file. I am unable to fiugure out why grid data is omiting data on corner. See the image attached. I plotted 3d scttered data using plot3 comand to ensure there exist data, which is denoted by circles. I have 403 nodes and its x,y,z coordinates.

my programme is as follows.

x=disp(:,1); %x-cordinates of data point
y=disp(:,2); %y-cordinates of data point
z=disp(:,3); %z-cordinates of data point
[xq,yq]=ndgrid(0:0.01:0.3, 0:0.005:0.06);%mesh grid 
vq= griddata(x,y,z,xq,yq);
figure
mesh(xq,yq,vq);
hold on;
plot3(x,y,z,'o');

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Walter Roberson 2018-11-21

difficult to say without the data .

Abhijeet Marekar 2018-11-21

在 MATLAB Online 中打开

My professor helped me with the problem. Matrix generated by ''griddata'' had 'NaN' values at some boundary points. These bounday points were outside of convex hull of griddata. I used ''scatteredInterpolant'' to extrapolate data and it worked.

m=0:0.01:0.3;
n=0:0.005:0.06;
[xq,yq] = ndgrid(x,y);
F = scatteredInterpolant(x,y,z,'nearest');
[a,b] = ndgrid(m,n);
vq = F(a,b);
figure
surf(a,b,vq);