Finding the closest coordinate from a surface plot based on a X, Y location

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Jorge Luis Paredes Estacio
评论： Voss 2024-8-20
Ran in:
Hello, I want to extrapolate a point (longitude,latitude) from the coordinates of a surface file (attached here as "slab_strike") as it is empty (Strike=NaN) when using interp2 as the points are outside the boundary. Despite I used the option "nearest", it is empty anyway.
% Coordinates of the points:
lat_GMM= -17.8990;
lon_GMM=-73.5295;
% The surface plot
load slab_strike % Loading the slab strike
Slab_strike.x=x;
Slab_strike.y=y;
Slab_strike.z=z;
Strike = interp2(Slab_strike.x,Slab_strike.y,Slab_strike.z,lon_GMM,lat_GMM)
Strike = NaN
As Strike=NaN, there is a way I can choose the closest point value from the surface avoiding any NaN value and select the closest non-NaN value.
I would appreciate the help

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采纳的回答

Voss
Voss 2024-8-16
移动：Torsten 2024-8-16
Ran in:
load slab_strike
is_ok = ~isnan(z);
[X,Y] = meshgrid(x,y);
X = X(is_ok);
Y = Y(is_ok);
Z = z(is_ok);
lon_GMM = -73.5295;
lat_GMM = -17.8990;
[~,idx] = min((X-lon_GMM).^2+(Y-lat_GMM).^2);
figure()
hold on
surf(x,y,z,'EdgeColor','none')
h1 = plot(lon_GMM,lat_GMM,'.r');
h2 = plot3(X(idx),Y(idx),Z(idx),'.k');
legend([h1 h2],{'Requested Point','Nearest Non-NaN z'})
xlim(lon_GMM+[-5 5])
ylim(lat_GMM+[-5 5])
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更多回答（2 个）

Torsten
Torsten 2024-8-16
编辑：Torsten 2024-8-16
lat_GMM and lon_GMM are not within the rectangle in which data for z are supplied.
In this case, interp2 returns NaN because it does not extrapolate.
Choose lat_GMM and lon_GMM in the limits for x and y where values are given for z.
Else you could use
[~,idx] = min(abs(x-lon_GMM))
[~,idy] = min(abs(y-lat_GMM))
Strike = z(idy,idx)
But it seems that your z-matrix contains NaN values.
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Jorge Luis Paredes Estacio
Jorge Luis Paredes Estacio 2024-8-16
编辑：Jorge Luis Paredes Estacio 2024-8-16
Thank you for your replied. That is correct, the selection should be based of finding the closest point withouth having a NaN value in the Z coordinate. A NaN value won't be useful for my analysis. In other words, it should skip that coordinate and choose another until it provides a non-NaN value.
Torsten
Torsten 2024-8-16
Then try whether z is NaN in the 8 points surrounding (x(idx),y(idy)).
If this also doesn't work, test z for NaN in the 16 following points and so on.

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Matt J
Matt J 2024-8-16
编辑：Matt J 2024-8-16
F=griddedInterpolant({Slab_strike.x,Slab_strike.y},Slab_strike.z,'linear','nearest');
Strike = F(lon_GMM,lat_GMM);
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Torsten
Torsten 2024-8-16
编辑：Torsten 2024-8-16
@Jorge Luis Paredes Estacio
Thank you. The error dissapeared, but Strike provides a NaN value
Strike=NaN;
The z-value nearest to your latitude and longitude is NaN - the result you also got using interp2.
Jorge Luis Paredes Estacio
Jorge Luis Paredes Estacio 2024-8-16
I still have the issue in selecting the closest point and avoiding as the same time the selection of any NaN value if that is the case. Thank you for your help.

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