meshgrid and griddata usage and NaN results for griddata

Question

Arundhatee Talukdar 2011-11-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/20958-meshgrid-and-griddata-usage-and-nan-results-for-griddata

I am trying to use meshgrid and griddata for plotting vv values over x and y Where

vv= 10000*1 matrix where I stored the (z)values for my points in the plot

and my code is

 [X,Y]= meshgrid(1:100, 1:100);
x = rand(10000,1);  y = rand(10000,1);
ZI = griddata(x,y,vv,X,Y);
hold on
imshow(ZI, jet);
hold on

I am getting NaN for my ZI values. Why so?

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Answer 1

Seth DeLand 2011-11-11

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https://ww2.mathworks.cn/matlabcentral/answers/20958-meshgrid-and-griddata-usage-and-nan-results-for-griddata#answer_27722

在 MATLAB Online 中打开

The GRIDDATA function is trying to use the data in x,y,vv to fit a surface and then interpolate this surface at the points specified in X and Y.

The problem here is that x and y were created with RAND, so they are on the range 0<x<1 and 0<y<1. The points specified in X and Y are on the range 1<X<100 and 1<Y<100. So the range over which we are trying to interpolate has no defined values from the range that the surface was calculated.

A quick way to get some reasonable results would be to modify line 2 to be:

x = 100*rand(10000,1); y = 100*rand(10000,1);