How to ignore nan values in using trapz function

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Bijay Guha 2018-2-13

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编辑： Luis 2024-4-1

Hello.. I have two column matrix one is height another one is data, both are of same sizes. But both includes some NaN values.

height=[NaN;NaN;NaN;0.246;1.252;2.253;3.2470;4.228;5.192;6.139;7.072];
data=[NaN;NaN;NaN;NaN;NaN;0.0014428;0.0018342;0.0019822;0.0017613;0.0013172;NaN];

I want to integrate the data with respect to height, but as expected it gives NaN output, as the data contains NaN values. Actually the number of NaN is varying for different sets. So can anyone help in general way to omit this NaN element in using trapz function (just like nanmean, nansum, nanstd etc). Extrapolation will give error in my case, so I need answer without extrapolation. Any answer will be helpful. Thanks in advance

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采纳的回答

Birdman 2018-2-13

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https://ww2.mathworks.cn/matlabcentral/answers/382335-how-to-ignore-nan-values-in-using-trapz-function#answer_304864

编辑：Birdman 2018-2-13

在 MATLAB Online 中打开

Before evaluation, you can get rid of nans as follows:

height=height(~isnan(height))
data=data(~isnan(data))

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Torsten 2023-12-18

编辑：Torsten 2023-12-18

It's not possible that each function takes care about imported NaN values. You are the one who should "omitnan" whereever possible in your computations.

Luis 2024-4-1

编辑：Luis 2024-4-1

Even the following is still wrong, as it adds erroneous area where the ~nan segments are joined together:

dataNans = isnan(Data); heightNans = isnan(Height);

useIndicees = ~dataNans & ~heightNans

trapz(Data(useIndicees),Height(useIndicees))

(Consider e.g. integrating the area of a wall where x=data is along width, and nan's in y=height signify gaps in the wall. I won't show my ugly code here to take care of that, but may be you can come up with something elegant.)

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