Indexing into a type I don't recognize

Inherited code ... have a struct with an array of fields. One of the fields is called tag which is seems to be struct of strings (if I hover over the field only see the 1st value), if I use the command window then the output is a list of answers of type string. I'm able to search this list via ii = find(strcmp({ext_header.tag},'FS')==1) ... I now want to access the associated value in ext_header.value. If I create a cell array c = {ext_header.value}; then I can access the desired value using cell2mat(c(ii)).

This seems akward to me ... i.e. don't wish to create the cell array ... but I haven't been able to directly index into ext_header.value?

[Walter Roberson]

Please confirm that the data type is string (shows up with double quotes) and not character vectors. The code you are using is suitable for tag holding character vectors.

[Walter Roberson]

Are the values scalar? If so use [] instead of {}

[Douglas Farinelli]

Single quote. The values are scalars.

K>> ext_header.value[1]

ext_header.value[1]

↑

Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

K>> ext_header.value{1}

Expected one output from a curly brace or dot indexing expression, but there were 58 results.

K>> ext_header.value(1)

Expected one output from a curly brace or dot indexing expression, but there were 58 results.

[Stephen23]

"have a struct with an array of fields"

But your examples show a structure array with scalar fields. Please show the output of this command:

size(ext_header)

[Walter Roberson]

c = [ext_header.value];
c(ii)

But Stephen's idea to use ext_header(ii).value is a good one for the case of scalar ii

Answer 1

[Stephen23]

Use indexing to get any elements you want from a structure array:

ext_header(ii).value

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

Note that your attempt using an intermediate cell array would be much simpler and more efficient using the correct cell indexing (rather than that very awkward and slow cell2mat):

c = {ext_header.value};
c{ii}

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-cell-array.html