Accesing a field within a row of a data structure

Question

Mehdi Jaiem 2022-5-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1713185-accesing-a-field-within-a-row-of-a-data-structure

评论： Mehdi Jaiem 2022-5-6

I have the following code

A=[DS.Carb]>2700;
B=[DS.Vit]==1;
C=or(A,B);
Index=find(C==1);
M=[DS.User_ID(Index)];

As you can see I am trying to acces some parts of the datastructure DS and save some information deending on "Index"

for exaple if Index=[3 4 67 8] then I would like to extract the content of the User_ID corresponding to the index each time

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Answer 1

Voss 2022-5-6

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https://ww2.mathworks.cn/matlabcentral/answers/1713185-accesing-a-field-within-a-row-of-a-data-structure#answer_958570

在 MATLAB Online 中打开

The correct syntax for getting the User_ID of elements at indices Index of struct array DS would be

M = [DS(Index).User_ID];

or

M = {DS(Index).User_ID};

depending on the class of the data stored in field User_ID.

For example:

DS = struct( ...
    'User_ID',{1 2 3 4}, ...
    'Carb',{2600 2800 2600 2800}, ...
    'Vit',{0 0 1 1});
M = [DS([DS.Carb]>2700 | [DS.Vit]==1).User_ID]
M = 1×3
     2     3     4
DS = struct( ...
    'User_ID',{'one' 'two' 'three' 'four'}, ...
    'Carb',{2600 2800 2600 2800}, ...
    'Vit',{0 0 1 1});
M = {DS([DS.Carb]>2700 | [DS.Vit]==1).User_ID}
M = 1×3 cell array
    {'two'}    {'three'}    {'four'}