Trouble with struct indexing?

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?

Answer 1

[Walter Roberson]

The best approach is not to do that.

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Answer 2

[Matt J]

... 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

[Walter Roberson]

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