How to find the name of the first filed of a struct?

I have a structre which has some fields. How can I find the field name of the first field?

Here is the struct I have:

  struct with fields:

                   unpatterned_H_65_full: [17×34 table]
                  unpatterned_H_100_full: [17×34 table]
              unpatterned_H_100_ribboned: [17×34 table]
    unpatterned_H_100_ribboned_sectioned: [17×34 table]
              unpatterned_H_65_sectioned: [17×34 table]
             unpatterned_He_100_sectioned: [17×34 table]

I need to write a code that returns say " unpatterned_H_65_full".

Answer 1

[dpb]

If the struct variable is s, then

name=fieldnames(s);
name=name(1);

No way to write the second-level addressing w/o the intermediary/temporary variable comes to me for a one-liner.

[Walter Roberson]

You probably want

names = fieldnames(s);
name = names{1};

The easiest one-liner is to use an extra function such as

FirstCell = @(C) C{1};

name = FirstCell( fieldnames(s) );

It is possible to do a real one-line, but it uses some pretty ugly code.

[dpb]

"You probably want..."

I purposely used name both places to not have the extra temporary hanging around after... :)

[Walter Roberson]

Having names around permits you to examine additional fields less expensively.

In any case fieldnames returns a cell array of character vectors and indexing it with (1) would return a scalar cell instead of the character vector

[dpb]

1. Yes, if there were to be a need for other fields besides the stated need for only the first
2. Yes, but cellstr is oftentimes more convenient than char string--but, sometimes it isn't...OP didn't give any context to know how the result was/is to be used. :)