fromCsv returns a cannot open file exception - flutter

Question

I am trying to use the ml_algo package to get a dataset using the fromCsv method present in the ml_algo package. I have put the csv file into an asset folder and still get an error.
I have tried all possible ways from flutter clean to invalidate cache and restart and even tried putting it on my phone and I gave the absolute path still it does not work
The following is the dart code:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:ml_dataframe/ml_dataframe.dart';
import 'package:ml_preprocessing/ml_preprocessing.dart';
import 'package:ext_storage/ext_storage.dart';
import 'package:permission/permission.dart';
import 'package:path_provider/path_provider.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#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, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
Future<void> initialiseDataframe() async {
/* var permissionsRequested = await Permission.requestSinglePermission(PermissionName.Storage);
print(permissionsRequested);
var permissionsStatus = await Permission.getSinglePermissionStatus(PermissionName.Storage);
print(permissionsStatus.toString());
*/
Directory tempDir = await getTemporaryDirectory();
String tempdir = tempDir.absolute.path;
print(tempdir);
final String directory = await ExtStorage.getExternalStorageDirectory();
print(directory);
final dataFrame = await fromCsv('wheat.csv',
headerExists: true,
columns: [2,3,5,6,7,8,9,10,11,12,13,14,15,16,
17,18,19,20,21,22,23,24,25]);
final normaliser = Normalizer();
final transformedDataset = normaliser.process(dataFrame);
print(transformedDataset.toMatrix());
}
#override
void initState() {
initialiseDataframe();
}
}
and here is the pubspec.yaml file
name: linear_regression
description: A new Flutter application.
# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1
environment:
sdk: ">=2.1.0 <3.0.0"
dependencies:
flutter:
sdk: flutter
# The following adds the Cupertino Icons font to your application.
# Use with the CupertinoIcons class for iOS style icons.
cupertino_icons: ^0.1.2
ml_dataframe: ^0.0.11
ml_preprocessing: ^5.0.1
ml_algo: ^13.3.7
ext_storage: ^1.0.2
permission: ^0.1.5
path_provider: ^1.6.1
dev_dependencies:
flutter_test:
sdk: flutter
# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec
# The following section is specific to Flutter.
flutter:
# The following line ensures that the Material Icons font is
# included with your application, so that you can use the icons in
# the material Icons class.
uses-material-design: true
# To add assets to your application, add an assets section, like this:
assets:
- assets/res/wheat.csv
# - images/a_dot_ham.jpeg
# An image asset can refer to one or more resolution-specific "variants", see
# https://flutter.dev/assets-and-images/#resolution-aware.
# For details regarding adding assets from package dependencies, see
# https://flutter.dev/assets-and-images/#from-packages
# To add custom fonts to your application, add a fonts section here,
# in this "flutter" section. Each entry in this list should have a
# "family" key with the font family name, and a "fonts" key with a
# list giving the asset and other descriptors for the font. For
# example:
# fonts:
# - family: Schyler
# fonts:
# - asset: fonts/Schyler-Regular.ttf
# - asset: fonts/Schyler-Italic.ttf
# style: italic
# - family: Trajan Pro
# fonts:
# - asset: fonts/TrajanPro.ttf
# - asset: fonts/TrajanPro_Bold.ttf
# weight: 700
#
# For details regarding fonts from package dependencies,
# see https://flutter.dev/custom-fonts/#from-packages
and the error stack
E/flutter (26103): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: FileSystemException: Cannot open file, path = 'asset/res/wheat.csv' (OS Error: No such file or directory, errno = 2)
E/flutter (26103): #0 _File.open.<anonymous closure> (dart:io/file_impl.dart:366:9)
E/flutter (26103): #1 _rootRunUnary (dart:async/zone.dart:1134:38)
E/flutter (26103): #2 _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter (26103): #3 _FutureListener.handleValue (dart:async/future_impl.dart:139:18)
E/flutter (26103): #4 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:680:45)
E/flutter (26103): #5 Future._propagateToListeners (dart:async/future_impl.dart:709:32)
E/flutter (26103): #6 Future._completeWithValue (dart:async/future_impl.dart:524:5)
E/flutter (26103): #7 Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:554:7)
E/flutter (26103): #8 _rootRun (dart:async/zone.dart:1126:13)
E/flutter (26103): #9 _CustomZone.run (dart:async/zone.dart:1023:19)
E/flutter (26103): #10 _CustomZone.runGuarded (dart:async/zone.dart:925:7)
E/flutter (26103): #11 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:965:23)
E/flutter (26103): #12 _microtaskLoop (dart:async/schedule_microtask.dart:43:21)
E/flutter (26103): #13 _startMicrotaskLoop (dart:async/schedule_microtask.dart:52:5)
E/flutter (26103):

Answer 1

The problem is that you're trying to access a dataset by using its absolute path, but the path you used is wrong since it's altered during runtime. Unfortunately, Flutter doesn't provide us with the correct absolute path for its assets in runtime.
There is a solution of the issue in ml_algo 15.6.3 and ml_dataframe 0.4.0: you need to read your dataset asset using rootBundle.loadString and feed the resulting string to a DataFrame.fromRawCsv(...) constructor:
import 'package:flutter/services.dart' show rootBundle;
import 'package:ml_dataframe/ml_dataframe.dart';
final rawCsvContent = await rootBundle.loadString('assets/res/wheat.csv');
final samples = DataFrame.fromRawCsv(rawCsvContent);