how to solve extra text error when reading json files?

I am trying to read a json file from an arduino board in matlab with the following script:

% fileName = 'test1.json';            % filename in JSON extension 
% str = fileread(fileName);           % dedicated for reading files as text 
% data = jsondecode(str);             % Using the jsondecode function to parse JSON from string

but I get the following error:

Error using jsondecode JSON syntax error at line 1, column 79 (character 79): additional text. Error in read_json (line 4) data = jsondecode(str); % Using the jsondecode function to parse JSON from a string

I imagine it must be something with the quotes, commas or brackets...

I need to extract the acceleration values to use them in matlab later (acc_x, acc_y, and acc_z). The json fille is:

{"acc_x": 0.24, "acc_y": 0.78, "acc_z": 0.46, "Timestamp": 1691078254.4053023},
{"acc_x": 0.27, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4153075},
{"acc_x": 0.29, "acc_y": 0.78, "acc_z": 0.5, "Timestamp": 1691078254.43097},
{"gy_x": -35.89, "gy_y": 3.78, "gy_z": 14.4, "Timestamp": 1691078254.43097},
{"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4409742},
{"gy_x": -33.39, "gy_y": 2.62, "gy_z": 13.98, "Timestamp": 1691078254.4409742},
{"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.44, "Timestamp": 1691078254.4409742},
{"gy_x": -29.79, "gy_y": 1.83, "gy_z": 8.79, "Timestamp": 1691078254.4409742},
{"acc_x": 0.27, "acc_y": 0.8, "acc_z": 0.41, "Timestamp": 1691078254.456637},
{"gy_x": -25.57, "gy_y": -0.37, "gy_z": 7.51, "Timestamp": 1691078254.456637},
{"acc_x": 0.25, "acc_y": 0.82, "acc_z": 0.44, "Timestamp": 1691078254.4666882},
{"gy_x": -25.57, "gy_y": -1.65, "gy_z": 8.85, "Timestamp": 1691078254.4767776},
{"acc_x": 0.22, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.4767776},
{"gy_x": -28.81, "gy_y": -0.31, "gy_z": 11.29, "Timestamp": 1691078254.4767776},
{"acc_x": 0.23, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.486785},

Answer 1

[Voss]

% I had to change the extension to upload the file, so here I change it back:
movefile('test1.txt','test1.json')

Try this:

txt = fileread('test1.json')

txt = 
    '{"acc_x": 0.24, "acc_y": 0.78, "acc_z": 0.46, "Timestamp": 1691078254.4053023},
     {"acc_x": 0.27, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4153075},
     {"acc_x": 0.29, "acc_y": 0.78, "acc_z": 0.5, "Timestamp": 1691078254.43097},
     {"gy_x": -35.89, "gy_y": 3.78, "gy_z": 14.4, "Timestamp": 1691078254.43097},
     {"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4409742},
     {"gy_x": -33.39, "gy_y": 2.62, "gy_z": 13.98, "Timestamp": 1691078254.4409742},
     {"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.44, "Timestamp": 1691078254.4409742},
     {"gy_x": -29.79, "gy_y": 1.83, "gy_z": 8.79, "Timestamp": 1691078254.4409742},
     {"acc_x": 0.27, "acc_y": 0.8, "acc_z": 0.41, "Timestamp": 1691078254.456637},
     {"gy_x": -25.57, "gy_y": -0.37, "gy_z": 7.51, "Timestamp": 1691078254.456637},
     {"acc_x": 0.25, "acc_y": 0.82, "acc_z": 0.44, "Timestamp": 1691078254.4666882},
     {"gy_x": -25.57, "gy_y": -1.65, "gy_z": 8.85, "Timestamp": 1691078254.4767776},
     {"acc_x": 0.22, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.4767776},
     {"gy_x": -28.81, "gy_y": -0.31, "gy_z": 11.29, "Timestamp": 1691078254.4767776},
     {"acc_x": 0.23, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.486785},'

txt = ['[' txt(1:end-1) ']']

txt = 
    '[{"acc_x": 0.24, "acc_y": 0.78, "acc_z": 0.46, "Timestamp": 1691078254.4053023},
     {"acc_x": 0.27, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4153075},
     {"acc_x": 0.29, "acc_y": 0.78, "acc_z": 0.5, "Timestamp": 1691078254.43097},
     {"gy_x": -35.89, "gy_y": 3.78, "gy_z": 14.4, "Timestamp": 1691078254.43097},
     {"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.47, "Timestamp": 1691078254.4409742},
     {"gy_x": -33.39, "gy_y": 2.62, "gy_z": 13.98, "Timestamp": 1691078254.4409742},
     {"acc_x": 0.32, "acc_y": 0.78, "acc_z": 0.44, "Timestamp": 1691078254.4409742},
     {"gy_x": -29.79, "gy_y": 1.83, "gy_z": 8.79, "Timestamp": 1691078254.4409742},
     {"acc_x": 0.27, "acc_y": 0.8, "acc_z": 0.41, "Timestamp": 1691078254.456637},
     {"gy_x": -25.57, "gy_y": -0.37, "gy_z": 7.51, "Timestamp": 1691078254.456637},
     {"acc_x": 0.25, "acc_y": 0.82, "acc_z": 0.44, "Timestamp": 1691078254.4666882},
     {"gy_x": -25.57, "gy_y": -1.65, "gy_z": 8.85, "Timestamp": 1691078254.4767776},
     {"acc_x": 0.22, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.4767776},
     {"gy_x": -28.81, "gy_y": -0.31, "gy_z": 11.29, "Timestamp": 1691078254.4767776},
     {"acc_x": 0.23, "acc_y": 0.82, "acc_z": 0.46, "Timestamp": 1691078254.486785}]'

C = jsondecode(txt);

C{:} % check the contents of C

ans = struct with fields:
        acc_x: 0.2400
        acc_y: 0.7800
        acc_z: 0.4600
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2700
        acc_y: 0.7800
        acc_z: 0.4700
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2900
        acc_y: 0.7800
        acc_z: 0.5000
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -35.8900
         gy_y: 3.7800
         gy_z: 14.4000
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.3200
        acc_y: 0.7800
        acc_z: 0.4700
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -33.3900
         gy_y: 2.6200
         gy_z: 13.9800
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.3200
        acc_y: 0.7800
        acc_z: 0.4400
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -29.7900
         gy_y: 1.8300
         gy_z: 8.7900
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2700
        acc_y: 0.8000
        acc_z: 0.4100
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -25.5700
         gy_y: -0.3700
         gy_z: 7.5100
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2500
        acc_y: 0.8200
        acc_z: 0.4400
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -25.5700
         gy_y: -1.6500
         gy_z: 8.8500
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2200
        acc_y: 0.8200
        acc_z: 0.4600
    Timestamp: 1.6911e+09

ans = struct with fields:
         gy_x: -28.8100
         gy_y: -0.3100
         gy_z: 11.2900
    Timestamp: 1.6911e+09

ans = struct with fields:
        acc_x: 0.2300
        acc_y: 0.8200
        acc_z: 0.4600
    Timestamp: 1.6911e+09

[Tomás]

Thanks, I think this can help me!!

[Voss]

You're welcome!