Retrieve data from arbitrary point from contourf plot

Mechrod

2019 4 10

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Hi.

I'm plotting a x,y,T using 2D plot. Using the code below

[Xr,Yr,Tr] = griddata(x,y,T,unique(x),unique(y)','v4'); % http://www.alecjacobson.com/weblog/?p=1532
figure();
colormap(jet); 
[cc,hh]=contourf(Xr,Yr,Tr,'Showtext','on','LevelList',[400 600 700 800 900 1000 1100 1200 1300]);
hold on
colorbar; 
triplot(dt,'LineWidth',0.01,'color','k');
axis([0 0.006 0 0.003]);

i get this plot. But when i try to retrieve the T data from the plot, it always snaps to the nearest point of the grid data tha generated the plot.

Is there a way to retrive (programmatically) the T value from an arbitrary (x,y) position? Something like i have when using Tecplot (below), where i click the plot and it retrieves the interpolated values used the generate the image. My objective is to enter a x,y value and retrive the T value from that point.

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Mechrod 2019-4-10

在 MATLAB Online 中打开

I found a way that meets my requirements, after carefully reading the meshgrid and griddata help. I hope it can help someone else.

First i set up 2 vectors containing x and y positions of my points of interest, xp and yp. Then use griddata to generate interpolated values (Tp) for those positions. (Thats all i needed!)

x = pos_nos(:,1); % original data
y = pos_nos(:,2); 
T = pos_nos(:,3);
%
xp = [0.0001 ; 0.0008 ; 0.0014];
yp = [0.0001 ; 0.0008 ; 0.0014];
%
Tp = griddata(x,y,T,xp,yp,'natural');

After that, i can use meshgrid to generate a fine mesh where the results will be interpolated, in case i need to extract more data. Then i just use griddata and plot the image.

[xg,yg] = meshgrid(0:0.0001:0.006, 0:0.0001:0.004);
[Xr,Yr,Tr] = griddata(x,y,T,xg,yg,'natural');
figure();
colormap(jet); 
[cc,hh]=contourf(Xr,Yr,Tr,'Showtext','on','LevelList',[400 600 700 800 900 1000 1100 1200 1300]);