splitData helper added

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## 14.1.0
+- `Model selection`: `splitData` helper added
+
 ## 14.0.1
 - data splitters renamed and reorganized
 

lib/ml_algo.dart

@@ -10,5 +10,6 @@ export 'package:ml_algo/src/metric/classification/type.dart';
 export 'package:ml_algo/src/metric/metric_type.dart';
 export 'package:ml_algo/src/metric/regression/type.dart';
 export 'package:ml_algo/src/model_selection/cross_validator/cross_validator.dart';
+export 'package:ml_algo/src/model_selection/split_data.dart';
 export 'package:ml_algo/src/regressor/knn_regressor/knn_regressor.dart';
 export 'package:ml_algo/src/regressor/linear_regressor/linear_regressor.dart';

lib/src/model_selection/split_data.dart

@@ -9,28 +9,45 @@ List<DataFrame> splitData(DataFrame data, Iterable<num> ratios) {
       .rows
       .toList();
   var start = 0;
+  var ratioSum = 0.0;
 
   return ratios
       .map((ratio) {
         if (ratio <= 0 || ratio >= 1) {
-          throw Exception('Ratio value must be within range 0..1 (both '
+          throw Exception('Ratio value must be within the range 0..1 (both '
               'exclusive), $ratio given');
         }
 
-        final end = start + (inputRows.length * ratio).ceil();
+        ratioSum += ratio;
+
+        if (ratioSum >= 1) {
+          throw Exception('Ratios sum is more than or equal to 1');
+        }
+
+        final rawSplitSize = inputRows.length * ratio;
+
+        if (rawSplitSize < 1) {
+          throw Exception('Ratio is too small comparing to the input data size: '
+              'ratio $ratio, min ratio value '
+              '${(1 / inputRows.length).toStringAsFixed(2)}');
+        }
+
+        final end = start + (rawSplitSize.ceil() == inputRows.length
+            ? rawSplitSize.floor()
+            : rawSplitSize.ceil());
         final rows = inputRows.sublist(start, end);
 
         start = end;
 
-        return DataFrame(rows, headerExists: false, header: data.header);
+        return DataFrame(
+            rows,
+            headerExists: false,
+            header: data.header,
+        );
       })
-      .toList()
-      .followedBy([
-        DataFrame(
-          inputRows.sublist(start),
-          headerExists: false,
-          header: data.header
-        ),
-      ])
-      .toList(growable: false);
+      .toList()..add(DataFrame(
+        inputRows.sublist(start),
+        headerExists: false,
+        header: data.header
+      ));
 }

pubspec.yaml

@@ -1,6 +1,6 @@
 name: ml_algo
 description: Machine learning algorithms, Machine learning models performance evaluation functionality
-version: 14.0.1
+version: 14.1.0
 homepage: https://github.com/gyrdym/ml_algo
 
 environment:

test/model_selection/split_data_test.dart

@@ -57,5 +57,136 @@ void main() {
         [500981, 29918, 5008.55],
       ]);
     });
+
+    test('should split data, case 2', () {
+      final splits = splitData(data, [0.2, 0.2, 0.2, 0.2])
+          .toList();
+
+      expect(splits, hasLength(5));
+      expect(splits[0].header, header);
+      expect(splits[0].rows, [
+        [100.00, null, 200.33],
+      ]);
+      expect(splits[1].header, header);
+      expect(splits[1].rows, [
+        [-2221,  1002, 70009],
+      ]);
+      expect(splits[2].header, header);
+      expect(splits[2].rows, [
+        [ 9008, 10006,  null],
+      ]);
+      expect(splits[3].header, header);
+      expect(splits[3].rows, [
+        [  7888, 10002,  300918],
+      ]);
+      expect(splits[4].header, header);
+      expect(splits[4].rows, [
+        [500981, 29918, 5008.55],
+      ]);
+    });
+
+    test('should throw exception if there is a too small ratio, case 1', () {
+      expect(() => splitData(data, [0.2, 0.3, 0.01]), throwsException);
+    });
+
+    test('should throw exception if there is a too small ratio, case 2', () {
+      expect(() => splitData(data, [0.2, 0.3, 0.1]), throwsException);
+    });
+
+    test('should split data into two parts, first part is less than the '
+        'second one', () {
+      final splits = splitData(data, [0.2])
+          .toList();
+
+      expect(splits, hasLength(2));
+      expect(splits[0].header, header);
+      expect(splits[0].rows, [
+        [100.00, null, 200.33],
+      ]);
+      expect(splits[1].header, header);
+      expect(splits[1].rows, [
+        [ -2221,  1002,   70009],
+        [  9008, 10006,    null],
+        [  7888, 10002,  300918],
+        [500981, 29918, 5008.55],
+      ]);
+    });
+
+    test('should split data into two parts, first part is less than the '
+        'second one, case 2', () {
+      final splits = splitData(data, [0.25])
+          .toList();
+
+      expect(splits, hasLength(2));
+      expect(splits[0].header, header);
+      expect(splits[0].rows, [
+        [100.00, null, 200.33],
+        [-2221,  1002,  70009],
+      ]);
+      expect(splits[1].header, header);
+      expect(splits[1].rows, [
+        [  9008, 10006,    null],
+        [  7888, 10002,  300918],
+        [500981, 29918, 5008.55],
+      ]);
+    });
+
+    test('should split data into two parts, first part is greater than the '
+        'second one', () {
+      final splits = splitData(data, [0.9])
+          .toList();
+
+      expect(splits, hasLength(2));
+      expect(splits[0].header, header);
+      expect(splits[0].rows, [
+        [100.00,  null, 200.33],
+        [ -2221,  1002,  70009],
+        [  9008, 10006,   null],
+        [  7888, 10002, 300918],
+      ]);
+      expect(splits[1].header, header);
+      expect(splits[1].rows, [
+        [500981, 29918, 5008.55],
+      ]);
+    });
+
+    test('should split data into two parts, first part is greater than the '
+        'second one, case 2', () {
+      final splits = splitData(data, [0.95])
+          .toList();
+
+      expect(splits, hasLength(2));
+      expect(splits[0].header, header);
+      expect(splits[0].rows, [
+        [100.00,  null, 200.33],
+        [ -2221,  1002,  70009],
+        [  9008, 10006,   null],
+        [  7888, 10002, 300918],
+      ]);
+      expect(splits[1].header, header);
+      expect(splits[1].rows, [
+        [500981, 29918, 5008.55],
+      ]);
+    });
+
+    test('should throw exception if ratios sum is equal to 1, '
+        '2 elements', () {
+      expect(() => splitData(data, [0.5, 0.5]), throwsException);
+    });
+
+    test('should throw exception if ratios sum is equal to 1, '
+        '3 elements', () {
+      expect(() => splitData(data, [0.3, 0.3, 0.4]), throwsException);
+    });
+
+    test('should throw exception if ratios sum is greater than 1, '
+        '2 elements', () {
+      expect(() => splitData(data, [0.5, 0.6]), throwsException);
+    });
+
+    test('should throw exception if ratios sum is greater than 1, '
+        '3 elements', () {
+      expect(() => splitData(data, [0.3, 0.5, 0.4]), throwsException);
+    });
   });
 }