Offer suggestions for possibly mistyped label column names

Author: Crabzmatic

src/Microsoft.ML.AutoML/Utils/StringEditDistance.cs

@@ -0,0 +1,60 @@
+using System;
+
+namespace Microsoft.ML.AutoML.Utils
+{
+    public static class StringEditDistance
+    {
+        public static int GetEditDistance(string first, string second)
+        {
+            if (first is null)
+            {
+                throw new ArgumentNullException(nameof(first));
+            }
+
+            if (second is null)
+            {
+                throw new ArgumentNullException(nameof(second));
+            }
+
+            if (first.Length == 0 || second.Length == 0)
+            {
+                return first.Length + second.Length;
+            }
+
+            var currentRow = 0;
+            var nextRow = 1;
+            var rows = new int[second.Length + 1, second.Length + 1];
+
+            for (var j = 0; j <= second.Length; ++j)
+            {
+                rows[currentRow, j] = j;
+            }
+
+            for (var i = 1; i <= first.Length; ++i)
+            {
+                rows[nextRow, 0] = i;
+                for (var j = 1; j <= second.Length; ++j)
+                {
+                    var deletion = rows[currentRow, j] + 1;
+                    var insertion = rows[nextRow, j - 1] + 1;
+                    var substitution = rows[currentRow, j - 1] + (first[i - 1].Equals(second[j - 1]) ? 0 : 1);
+
+                    rows[nextRow, j] = Math.Min(deletion, Math.Min(insertion, substitution));
+                }
+
+                if (currentRow == 0)
+                {
+                    currentRow = 1;
+                    nextRow = 0;
+                }
+                else
+                {
+                    currentRow = 0;
+                    nextRow = 1;
+                }
+            }
+
+            return rows[currentRow, second.Length];
+        }
+    }
+}

src/Microsoft.ML.AutoML/Utils/UserInputValidationUtil.cs

@@ -6,6 +6,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using Microsoft.ML.AutoML.Utils;
 using Microsoft.ML.Data;
 
 namespace Microsoft.ML.AutoML
@@ -248,6 +249,11 @@ private static void ValidateTrainDataColumn(IDataView trainData, string columnNa
             var nullableColumn = trainData.Schema.GetColumnOrNull(columnName);
             if (nullableColumn == null)
             {
+                var closestNamed = ClosestNamed(trainData, columnName, 2);
+                if (closestNamed != string.Empty)
+                {
+                    throw new ArgumentException($"Provided {columnPurpose} column '{columnName}' not found in training data. Did you mean '{closestNamed}'.");
+                }
                 throw new ArgumentException($"Provided {columnPurpose} column '{columnName}' not found in training data.");
             }
 
@@ -272,6 +278,23 @@ private static void ValidateTrainDataColumn(IDataView trainData, string columnNa
             }
         }
 
+        private static string ClosestNamed(IDataView trainData, string columnName, int maxAllowableEditDistance = int.MaxValue)
+        {
+            var minEditDistance = int.MaxValue;
+            var closestNamed = string.Empty;
+            foreach (var column in trainData.Schema)
+            {
+                var editDistance = StringEditDistance.GetEditDistance(column.Name, columnName);
+                if (editDistance < minEditDistance)
+                {
+                    minEditDistance = editDistance;
+                    closestNamed = column.Name;
+                }
+            }
+
+            return minEditDistance <= maxAllowableEditDistance ? closestNamed : string.Empty;
+        }
+
         private static string FindFirstDuplicate(IEnumerable<string> values)
         {
             var groups = values.GroupBy(v => v);

test/Microsoft.ML.AutoML.Tests/UserInputValidationTests.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.ML.Data;
 using Microsoft.ML.TestFramework;
@@ -50,6 +51,21 @@ public void ValidateExperimentExecuteLabelNotInTrain()
             }
         }
 
+        [Fact]
+        public void ValidateExperimentExecuteLabelNotInTrainMistyped()
+        {
+            foreach (var task in new[] { TaskKind.Recommendation, TaskKind.Regression, TaskKind.Ranking })
+            {
+                var originalColumnName = _data.Schema.First().Name;
+                var mistypedColumnName = originalColumnName + "a";
+                var ex = Assert.Throws<ArgumentException>(() => UserInputValidationUtil.ValidateExperimentExecuteArgs(_data,
+                    new ColumnInformation() { LabelColumnName = mistypedColumnName }, null, task));
+
+                Assert.Equal($"Provided label column '{mistypedColumnName}' not found in training data. Did you mean '{originalColumnName}'.",
+                    ex.Message);
+            }
+        }
+
         [Fact]
         public void ValidateExperimentExecuteNumericColNotInTrain()
         {