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Convert Struct to Readable JSON(Pretty Print)

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Every struct I pass to jsonecode gets converted to a 1 by N char array with no newline chacters. Therefore, when I export the json as to a text file I only have one line. The file is not easly readble because I have to scroll the JSON text horizontaly. How can I make jsonencode's output easily readable(pretty print)?
I get this.
{ "firstName": "John", "lastName": "Smith", "age": 25, "address": { "streetAddress": "3 Apple Hill Dr", "city": "Natick", "state": "MA", "postalCode": "01760" }, "phoneNumber": [ { "type": "home", "number": "123 456 7890" }, { "type": "cell", "number": "098 765 4321" } ] }
I want something like this.
"firstName": "John",
"lastName": "Smith",
"age": 25,
"streetAddress": "3 Apple Hill Dr",
"city": "Natick",
"state": "MA",
"postalCode": "01760"
"type": "home",
"number": "123 456 7890"
"type": "cell",
"number": "098 765 4321"
Davide Serina
Davide Serina on 8 Dec 2022
Moved: DGM on 8 Dec 2022
ciao, come si fa ad ottenere una struttura come quella che hai scritto partendo da una struttura su matlab?! cioè non riesco a fare gli annidamenti. bisogna usare un ciclo for???
Sean Bone
Sean Bone on 9 Dec 2022
Ciao @Davide Serina, la tua domanda si riferisce a come creare una struttura annidata in MATLAB o a come convertire una struttura annidata in JSON? Oppure ancora a come convertire una struttura MATLAB in JSON con le indentature per rappresentare gli annidamenti?

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Accepted Answer

Sean Bone
Sean Bone on 30 Jan 2022
In more recent Matlab versions, you can do the following:
jsonencode(data, "PrettyPrint", true);
Note that this option was only introduced in Matlab R2021a, despite the documentation for jsonencode not mentioning this explicitly.
  1 Comment
ILoveMATLAB on 17 May 2022
I guess I will accept this anwser; although, I was using an older version of matlab when I wrote this question.

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More Answers (2)

Robin Larsson Nordström
Robin Larsson Nordström on 3 Oct 2023
Edited: Robin Larsson Nordström on 3 Oct 2023
For the provided example the default pretty print output will be fine:
txt=jsonencode(data, "PrettyPrint", true);
However if the input data struct contains fields with vectors or matrices the jsonencode PrettyPrint in Matlab 2023b adds a newline for each element, making the encoded text hard to read even when the number of elements are not that many.
Post-processing the output with a few regexprep lines to remove white-spaces inside vectors and matrices have worked well for me. Example below with the struct from the Matlab help on jsonencode PrettyPrint example with the addition of an extra field Q storing a 4 X 4 matrix:
s.Width = 800;
s.Height = 600;
s.Title = 'View from the 15th Floor';
s.Animated = false;
s.IDs = [116, 943, 234, 38793];
s.Q = round(randn(4),3);
txt =
'{ "Width": 800, "Height": 600, "Title": "View from the 15th Floor", "Animated": false, "IDs": [ 116, 943, 234, 38793 ], "Q": [ [ 0.104, -1.164, -2.504, 1.22 ], [ -0.277, -1.496, 0.394, 2.864 ], [ 0.418, 0.155, -0.266, 0.515 ], [ 1.536, 0.02, 0.071, 1.06 ] ] }'
% remove white-spaces inside vectors and matrices
txt = regexprep(txt,',\s+(?=\d)',','); % , white-spaces digit
txt = regexprep(txt,',\s+(?=-)',','); % , white-spaces minussign
txt = regexprep(txt,'[\s+(?=\d)','['); % [ white-spaces digit
txt = regexprep(txt,'[\s+(?=-)','['); % [ white-spaces minussign
txt = regexprep(txt,'(?<=\d)\s+]',']'); % digit white-spaces ]
txt =
'{ "Width": 800, "Height": 600, "Title": "View from the 15th Floor", "Animated": false, "IDs": [116,943,234,38793], "Q": [ [0.104,-1.164,-2.504,1.22], [-0.277,-1.496,0.394,2.864], [0.418,0.155,-0.266,0.515], [1.536,0.02,0.071,1.06] ] }'

Gaurav Garg
Gaurav Garg on 20 Nov 2019
You can find a function which can help you resolve the problem you are facing in this file.
  1 Comment
Laurel Keyes
Laurel Keyes on 28 Jun 2021
This file is helpful but not if you have nested structures. I use a quick and dirty method, where you just string-replace the commas or brackets like so:
% assuming your structure is saved to val:
str = jsonencode(val);
% add a return character after all commas:
new_string = strrep(str, ',', ',\n');
% add a return character after curly brackets:
new_string = strrep(new_string, '{', '{\n')
% etc...
% Write the string to file
fid = fopen("filename.json",'w')
fprint(fid, new_string);
This method will not indent but does allow a slightly better formatting, no matter the structure of your json

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