Cannot obtain structure elements where both field and variable are indexed into

Say I have a structure of students' information, where the indexing of both the name field and the structure itself are of interest:

>> students(1).name='john'

students = 

  1×2 struct array with fields:

    name

>> students(2).name='andrea'

students = 

  1×2 struct array with fields:

    name

Say I want to obtain the initial of several students' names. One student at a time, this works fine:

>> students(1).name(1)

ans =

    'j'

>> students(2).name(1)

ans =

    'a'

Also fine is if I call up the entire field:

>> students(1:2).name

ans =

  1×1 cell array

    {'john'}


ans =

  1×1 cell array

    {'andrea'}

But when I index into the structure AND the field name, this produces the notorious error:

>> students(1:2).name(1)
Expected one output from a curly brace or dot indexing expression, but there were 2 results.

Various forum threads suggest the structure or its field need to be encapsulated in square brackets, but this still did not work. If I do this with cell arrays, it also does not help.

I've hit this problems numerous times and always get around it with for loops, but in my current script I'd have to do this many times, and it'd be very helpful to know what the right syntax is for obtaining this sort of nested indexing, if there is one.

[dpb]

But when I index into the structure AND the field name, this produces the notorious error:

>> students(1:2).name(1)
Expected one output from a curly brace or dot indexing expression, but there were 2 results.

Why would there be more than one name for a given student? Looks to me like there's where the breakdown is...unless you've tried to store the first,last, middle initial as elements of an array instead as separate fields?

Fixing that would resolve the problem it would seem...

[z8080]

"Why would there be more than one name for a given student?"

There isn't. There's only one name for each student, in my example. With that line of code I was hoping to obtain ['j', 'a'] or some similar variable that contains the first element of the name field for each of the first and second elements of the student array.

[Stephen23]

"Various forum threads suggest the structure or its field need to be encapsulated in square brackets,"

Which ones? Please give link/s so that I can make corrections to those threads.

It is not possible to index into both the structure and the field simultaneously (except in the trivial case that the structure indexing returns a scalar structure), so any thread claiming that brackets or curly braces are "needed" is not correct.

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[z8080]

I tried to look for those threads I saw but could not find them/it. I could well have misinterpreted that they were suggesting it is possible to index into both the structure and the field simultaneously. I now understand this to require a for loop, or to employ arrayfun, as Turlough Hughes suggested

Answer 1

[Turlough Hughes]

Try the following:

students(1).name='john';
students(2).name='andrea';

arrayfun(@(x) students(x).name(1), 1:2).'

ans = 2×1 char array
    'j'
    'a'

[z8080]

Thanks a lot Turlough, that's what I was looking for!