Trouble with struct indexing?

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Daniel Montgomery
评论： Walter Roberson 2020-6-2
I have a struct with multiple fields that looks similar to this
Row field field2
1 ### ###
2 ### ###
3 ### ###
...
2000 ### ###
I get an error message when I type matrix.field{b} to access a single element of field2
in a loop for b=100, what is the correct notation to access a signle struct element in a loop?

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回答（2 个）

Walter Roberson
Walter Roberson 2020-6-1
Matt J
Matt J 2020-6-1
编辑：Matt J 2020-6-1
... to access a single element of field2.
The layout of your struct variable is not clear. If, for example, you have a scalar struct of the following form,
matrix.Row=1:3;
matrix.field1=4:6;
matrix.field2={4,5,6};
then this is the notation that you would use to extract the third element of field2,
>> b=3; matrix.field2{b}
ans =
6
This does not work for field1, because the contents of field1 is not a cell array,
>> b=3; matrix.field1{b}
Brace indexing is not supported for variables of this type.
However, ()-indexing will work as desired,
>> b=3; matrix.field1(b)
ans =
6
  1 个评论
Walter Roberson
Walter Roberson 2020-6-2
I believe that they were hoping that
b=2;
matrix.field{b}
would access matrix.field2
but it is not completely clear. Possibly they have a nonscalar structure and were looking for matrix(b).field2

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