How to check if a element of a struct is empty?

Question

Benson Gou 2020-10-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/613956-how-to-check-if-a-element-of-a-struct-is-empty

评论： Ameer Hamza 2020-10-15

Dear All,

I defined a struct and initialize it in the following way.

Res_All_Meas = struct([]);

[Res_All_Meas(1000).ind] = 0;

[Res_All_Meas(1000).res] = 0;

[Res_All_Meas(1000).xline] = 0;

[Res_All_Meas(1000).colnum] = 0;

Now in an iteration, I want to check if Res_All_Meas(i) is empty or not. If it is empty, I will assign some valeus to it.

Thanks a lot.

Benson

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Benson Gou 2020-10-14

编辑：Benson Gou 2020-10-14

Yes, I want to check if the field contents are empty. The field contents for Res_All_Meas(i) are zero before Res_all_Meas(i) is assigned a value. But how?

Thanks.

Beneon

Stephen23 2020-10-15

"I want to check if the field contents are empty."

See my answer.

"The field contents for Res_All_Meas(i) are zero before Res_all_Meas(i) is assigned a value."

Not in your example. What you showed has all fields of every structure element Res_All_Meas(1:999) containing empty numeric arrays, and the last element Res_All_Meas(1000) for which each field contains 0.

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Answer 1

Ameer Hamza 2020-10-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/613956-how-to-check-if-a-element-of-a-struct-is-empty#answer_514041

You can use isempty(): https://www.mathworks.com/help/matlab/ref/isempty.html

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Benson Gou 2020-10-14

I used isempty and tried several ways, but does not work. I think the isempty() works for number arrays.

Thanks a lot.

Benson

Ameer Hamza 2020-10-15

在 MATLAB Online 中打开

You need to apply isempty on a particular field of a struct. Something like this

tf = ismpty(Res_All_Meas(1).ind)

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Answer 2

Stephen23 2020-10-15

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/613956-how-to-check-if-a-element-of-a-struct-is-empty#answer_514338

编辑：Stephen23 2020-10-15

在 MATLAB Online 中打开

fun = @(s) all(structfun(@isempty,s)); % check the fields of a scalar structure.
idx = arrayfun(fun,Res_All_Meas); % indices of those structure elements with ALL fields empty.