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

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Mr M.
Mr M. 2018-10-16
评论： madhan ravi 2018-10-16
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?
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Stephen23
Stephen23 2018-10-16
编辑：Stephen23 2018-10-16
"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 2018-10-16
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Guillaume
Guillaume 2018-10-16
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)

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