How to check the existance of a struct field at a given index?

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Mr M.
Mr M. 2018 年 10 月 16 日
コメント済み: madhan ravi 2018 年 10 月 16 日
p(1).name = 'name1'; p(1).value = 1:10; p(2).name = 'name2';
I want to check existance of p(2).value, but exist and empty is not working for me. How to do?
  3 件のコメント
Mr M.
Mr M. 2018 年 10 月 16 日
exist('p(2).name')
ans =
0
Stephen23
Stephen23 2018 年 10 月 16 日
編集済み: Stephen23 2018 年 10 月 16 日
"I want to check existance of p(2).value, but exist and empty is not working for me. How to do?"
Every element of a structure array has the same fields. So if you have defined this:
p(1).name = 'name1';
p(1).value = 1:10;
p(2).name = 'name2';
Then by definition of a non-scalar structure the field p(2).value also exists. If you have not allocated it a value, then it will be initialized to the empty array. This means it is not clear what your question relates to:
  • p(2).value exists because it was created as soon as you created p(1).value. So testing for its existence is entirely superfluous.
  • The value of that field is []. Is that what you want to test for?
Note that exist is totally irrelevant to this problem.
empty is not a suitable MATLAB function: did you mean isempty ?

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madhan ravi
madhan ravi 2018 年 10 月 16 日
  5 件のコメント
Guillaume
Guillaume 2018 年 10 月 16 日
Important: as hinted by madhan's answer, the function used to test for emptiness is isempty, not empty (a completely different function that only works for classes). So instead of
empty(p(2).value)
use
isempty(p(2).value)
madhan ravi
madhan ravi 2018 年 10 月 16 日
Thank you Guillaume

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