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

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

[Stephen Cobeldick]

"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;

The indexing into Res_All_Meas(1000) refers to one single element of Res_All_Meas, so the square brackets are not required.

"I want to check if Res_All_Meas(i) is empty or not."

By definition one element of an array (which includes numeric, char, cell, and structure) has size 1x1(x1x1x1...) and so cannot be empty, one element is always scalar.

Do you really want to check if the field contents are empty?

[Benson Gou]

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

[Stephen Cobeldick]

"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.

Answer 1

[Ameer Hamza]

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

[Benson Gou]

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]

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

tf = ismpty(Res_All_Meas(1).ind)

Answer 2

[Stephen Cobeldick]

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.