How to exclude empty values from an array during statitical calculations?

Question

Emerson De Souza 2011-8-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/14666-how-to-exclude-empty-values-from-an-array-during-statitical-calculations

评论： Jon 2018-10-23

采纳的回答： Oleg Komarov

I have an array build of numbers and empty values NaN and I want to

calculate statistical quantities such as median, mean, etc... but not

including the NaN in the calculation.

For example, the median of the following array

NaN

1.14353916977288

1.13195167986180

NaN

1.27935109630269

NaN

1.15339038040937

NaN

equals NaN because most of the array elements are NaN. But my

intention was to calculate the median ONLY of the elements with

values (in this particular case, the median of only 4 elements).

I wonder if someone could tell me how to exclude NaN from the

calculation without need to change the Matrix.

Thank you

Emerson

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Answer 1

Oleg Komarov 2011-8-28

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/14666-how-to-exclude-empty-values-from-an-array-during-statitical-calculations#answer_19924

在 MATLAB Online 中打开

Look at the function isnan.

A = [NaN; NaN; 1.14353917; 1.13195168; NaN; NaN; 1.279351096; NaN; 1.15339038; NaN]
median(A(~isnan(A)))

Also, if you have the statistics toolbox look at nanmedian and similar.

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Jon 2018-10-23

An alternative is to use the optional nanflag argument to median, as indicated in the documentation for median "M = median(___,nanflag) optionally specifies whether to include or omit NaN values in the median calculation for any of the previous syntaxes. For example, median(A,'omitnan') ignores all NaN values in A."

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