'diabetes_classifier.json' (OS Error: Read-only file system, errno = 30)

[stephentandjiria]

Hi, I have been trying to replicate the example here, but I cannot write the json classifier model due to the following error:

Running "flutter pub get" in logistic_regressor...
Launching lib\main.dart on sdk gphone x86 in debug mode...
Running Gradle task 'assembleDebug'...
√  Built build\app\outputs\flutter-apk\app-debug.apk.
Installing build\app\outputs\flutter-apk\app.apk...
Debug service listening on ws://127.0.0.1:64760/6bAEB-pabM4=/ws
Syncing files to device sdk gphone x86...
I/flutter ( 7530): accuracy on k fold validation: 0.63
I/flutter ( 7530): 0.76
E/flutter ( 7530): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: FileSystemException: Cannot create file, path = 'diabetes_classifier.json' (OS Error: Read-only file system, errno = 30)
E/flutter ( 7530): #0      _File.create.<anonymous closure> (dart:io/file_impl.dart:255:9)
E/flutter ( 7530): #1      _rootRunUnary (dart:async/zone.dart:1362:47)
E/flutter ( 7530): #2      _CustomZone.runUnary (dart:async/zone.dart:1265:19)
E/flutter ( 7530): <asynchronous suspension>
E/flutter ( 7530): #3      SerializableMixin.saveAsJson (package:ml_algo/src/common/serializable/serializable_mixin.dart:9:18)
E/flutter ( 7530): <asynchronous suspension>
E/flutter ( 7530): #4      _MyHomePageState.trainModel (package:logistic_regressor/main.dart:99:5)
E/flutter ( 7530): <asynchronous suspension>
E/flutter ( 7530): 

I have tried using permission in android/app/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.logistic_regressor">
    <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

and also requested the permission via Permission.manageExternalStorage.request() in my main.dart:

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:ml_algo/ml_algo.dart';
import 'package:ml_dataframe/ml_dataframe.dart';
import 'package:ml_preprocessing/ml_preprocessing.dart';
import 'package:flutter/services.dart' show rootBundle;

import 'package:permission_handler/permission_handler.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  void trainModel() async {
    final rawCsvContent = await rootBundle.loadString('datasets/pima_indians_diabetes_database.csv');
    final samples = DataFrame.fromRawCsv(rawCsvContent);

    // === Prepare Dataset ===
    final targetColumnName = 'class variable (0 or 1)';

    final splits = splitData(samples, [0.7]);
    final validationData = splits[0];
    final testData = splits[1];

    // === Setup model selection algorithm ===
    final validator = CrossValidator.kFold(validationData, numberOfFolds: 5);

    final createClassifier = (DataFrame samples) =>
        LogisticRegressor(
          samples,
          targetColumnName,
          optimizerType: LinearOptimizerType.gradient,
          iterationsLimit: 90,
          learningRateType: LearningRateType.decreasingAdaptive,
          batchSize: samples.rows.length,
          probabilityThreshold: 0.7,
          collectLearningData: true,
        );

    // === Evaluate model performance ===
    final scores = await validator.evaluate(createClassifier, MetricType.accuracy);
    final accuracy = scores.mean();
    print('accuracy on k fold validation: ${accuracy.toStringAsFixed(2)}');

    final testSplits = splitData(testData, [0.8]);
    final classifier = createClassifier(testSplits[0]);
    final finalScore = classifier.assess(testSplits[1], MetricType.accuracy);

    print(finalScore.toStringAsFixed(2)); // approx. 0.75

    // === Write the model to JSON file ===
    var status = await Permission.manageExternalStorage.status;
    if (status.isDenied) {
      await Permission.manageExternalStorage.request();
    }

    await classifier.saveAsJson('diabetes_classifier.json');
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    trainModel();
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Plugin example app'),
        ),
        body: new Center(
          child: new Column(children: <Widget>[
            new Text('Running'),
          ]),
        ),
      ),
    );
  }
}

If anyone got insight on what the problem is, I would really appreciate if you could help.
Cheers!

[gyrdym]

@stephentandjiria Hi! It looks like you have some problems with permissions in your file system, the issue isn't connected to the library

[stephentandjiria]

@gyrdym I am still unsure on what's going on, but thanks anyway for the help!