scatteredInterpolant gives out NaN in some query points

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Philipp
Philipp 2023-8-9
评论： Philipp 2023-8-9
I have 3D-scattered testbench-data with x, y und z as setpoints and I want to make contourf-plots over x and y with z as adjustible parameter.
First i filtered and deleted doubled samples to make sure the datapoints are unique:
% Load Data
load('data.mat');
% Keep unique Data
setpoints = [data.x data.y data.z];
[setpointsu,idx] = unique(setpoints,'rows');
datau = data(idx,:);
Next I defined query-points which grid the room of the scattered data and interpolated:
xq = -50:5:0;
yq = 0:5:30;
zq = 25:5:75;
% Interpolieren
[Xq,Yq,Zq] = meshgrid(xq,yq,zq);
F.Value = scatteredInterpolant(x,y,z,datau.Value,'linear');
P.Value = F.Value(Xq,Yq,Zq);
But unfourtunately P.Value has some NaNs in the middle of the 'query room':
At these Points enough scattered input data should be availabe for interpolation.
What else could be causes for these red circled NaNs?
Thanks for your help.

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采纳的回答

Bruno Luong
Bruno Luong 2023-8-9
编辑：Bruno Luong 2023-8-9
Probably your data contains NaN at one or several points.
I don't quite understand your code
datau.Value
seems not valid since datau = data(idx,:); looks like an array.
Please share your data.
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Bruno Luong
Bruno Luong 2023-8-9
编辑：Bruno Luong 2023-8-9
Ran in:
Clearly you have point outside the convexhull AND you have NaN in your data (double check is not enough, quadriple check may be)
load('data.mat')
% Keep unique Data
x=data.x;
y=data.y;
z=data.z;
setpoints = [data.x data.y data.z];
[setpointsu,idx] = unique(setpoints,'rows');
datau = data(idx,:);
xq = -50:5:0;
yq = 0:5:30;
zq = 25:5:75;
% Interpolieren
[Xq,Yq,Zq] = meshgrid(xq,yq,zq);
find(isnan(datau.Value))
ans = 12×1
111 112 113 114 115 116 117 118 119 120
F.Value = scatteredInterpolant(x,y,z,datau.Value,'linear');
P.Value = F.Value(Xq,Yq,Zq);
xq = -50:5:0;
yq = 0:5:30;
zq = 25:5:75;
% Interpolieren
[Xq,Yq,Zq] = meshgrid(xq,yq,zq);
F.Value = scatteredInterpolant(x,y,z,datau.Value,'linear','nearest');
P.Value = F.Value(Xq,Yq,Zq);
P.Value(:,:,4)
ans = 7×11
0.4071 NaN NaN NaN 0.3632 0.4854 0.5979 0.5267 0.4373 0.3391 0.2409 NaN NaN NaN NaN 0.3955 0.4464 0.5515 0.5318 0.5121 0.4251 0.3269 NaN NaN NaN NaN 0.4262 0.4805 0.5317 0.4999 0.4682 0.4420 0.4172 NaN NaN NaN NaN 0.4182 0.3835 0.3556 0.4224 0.4003 0.3738 0.4393 0.5506 0.5072 0.4636 0.4433 0.4093 0.3093 0.1971 0.2639 0.3299 0.3920 0.4541 0.5508 0.5441 0.5064 0.4423 0.3797 0.3150 0.3080 0.2979 0.3229 0.3496 0.4106 0.5508 0.5463 0.5372 0.4609 0.3854 0.3785 0.4076 0.3975 0.3875 0.3774 0.3677
T=delaunayTriangulation(x,y,z);
F = convexHull(T);
close all
trisurf(F,x,y,z)
axis equal
hold on
plot3(Xq(:),Yq(:),Zq(:),'.')
Philipp
Philipp 2023-8-9
Your are right. Apologies. I checked the wrong column in my raw file.

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更多回答（1 个）

Walter Roberson
Walter Roberson 2023-8-9
By default, scatteredInterpolant with 'linear' method does not do extrapolation. If you attempt to query at a location that is outside the outside boundary of the triangulation of the reference points, then it would need extrapolation but that is not enabled by default for 'linear'
  1 个评论
Philipp
Philipp 2023-8-9
Thank you for your answer.
If I define ExtrapolationMethod as 'linear' there is no change in the outcome.
F.Value = scatteredInterpolant(x,y,z,datau.Value,'linear','linear');
The black x markers are showing the scattered input data points.

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