Access the data from a Struct

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Susan
Susan on 30 Mar 2020
Commented: Susan on 31 Mar 2020
I have a struct with fields
val = struct with fields:
abstract: [1×1 struct]
body_text: [72×1 struct]
when I extract the text data in body_text using "val.body_text.text" I got 72*1 struct. But when I try "A = val.abstract.text", I got only the first struct of the 72 structs. How can I put all these [72×1 struct] into A?
Thanks!
  3 Comments
Ameer Hamza
Ameer Hamza on 30 Mar 2020
''so val.abstract.text is either invalid reference or is the name of the 1x1 struct under val.abstract'''
Not necessarily. For example
>> s.text = '123';
s.xyz = 2;
val.abstract = s;
val.body_text = repmat(s, 1, 72);
>> val
val =
struct with fields:
abstract: [1×1 struct]
body_text: [1×72 struct]
>> val.abstract.text
ans =
'123'
Susan
Susan on 30 Mar 2020
Sorry for the confusion! What I meant was "But when I try "A = val.body_text.text", I got only the first struct of the 72 structs"

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Accepted Answer

Ameer Hamza
Ameer Hamza on 30 Mar 2020
Edited: Ameer Hamza on 30 Mar 2020
Try this, if the data in the field 'text' is scalar
A = [val.abstract.text];
If it is vector than try
A = {val.abstract.text};
  5 Comments
Ameer Hamza
Ameer Hamza on 31 Mar 2020
Try the following code. Place it one directly above the JSON files, or you can modify the first line according to the path of your JSON files. It will read all files, and gather their abstract.text and body_text.text fields into one struct. It then writes the final struct as a JSON file.
files = dir('JSON files/*.json');
s = struct('abstract', [], 'body_text', []);
for i=1:numel(files)
filename = fullfile(files(i).folder, files(i).name);
data = jsondecode(fileread(filename));
if ~isempty(data.abstract)
s.abstract = [s.abstract; cell2struct({data.abstract.text}, 'text', 1)];
end
if ~isempty(data.body_text)
s.body_text = [s.body_text; cell2struct({data.body_text.text}, 'text', 1)];
end
end
str = jsonencode(s);
f = fopen('filename.json', 'w');
fprintf(f, '%s', str);
fclose(f);
Susan
Susan on 31 Mar 2020
Thank you so much! I really appreciate your help.

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