Fixes #1242 Create Categories for symbology is inconsistent with larg…

…e datasets
DotSpatial · Dec 18, 2018 · 768af73 · 768af73
1 parent 15ab645
commit 768af73
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Showing 4 changed files with 13 additions and 6 deletions.
diff --git a/Changelog.md b/Changelog.md
@@ -148,4 +148,5 @@ Be aware that code written for 1.9 will not work out of the box because DotSpati
 - Error on OpenFile with special SPHEROID string (#1142)
 - Shape File Saves with Wrong DataTypes (#1005)
 - Calculation of translation param in InRamImageData.GetBitmap is defective (#1203)
-- MapImageLayer not drawn correctly on print (#1137)
+- MapImageLayer not drawn correctly on print (#1137)
+- Create Categories for symbology is inconsistent with large datasets (#1242)
diff --git a/Contributors b/Contributors
@@ -16,7 +16,7 @@ Jany
 Maxim Miroshnikov <mogikanin.tir@gmail.com>
 
 Contributors:
-Dan Ames
+Dan Ames <dan.ames@byu.edu>
 Darrel Brown
 Yang Cao
 Hugo Dejaune <hugo.dejaune@gmail.com>

diff --git a/Source/DotSpatial.Symbology/FeatureScheme.cs b/Source/DotSpatial.Symbology/FeatureScheme.cs
@@ -301,7 +301,8 @@ public void GetValues(IAttributeSource source, ICancelProgressHandler progressHa
                 pageSize = 10000;
                 int count = EditorSettings.MaxSampleCount;
 
-                Random rnd = new Random();
+                // Specified seed is required for consistently recreating the break values
+                Random rnd = new Random(9999);
                 AttributePager ap = new AttributePager(source, pageSize);
                 int countPerPage = count / ap.NumPages();
                 ProgressMeter pm = new ProgressMeter(progressHandler, "Sampling " + count + " random values", count);
@@ -385,7 +386,10 @@ public void GetValues(DataTable table)
                         Dictionary<int, double> randomValues = new Dictionary<int, double>();
                         int count = EditorSettings.MaxSampleCount;
                         int max = rows.Length;
-                        Random rnd = new Random();
+
+                        // Specified seed is required for consistently recreating the break values
+                        Random rnd = new Random(9999);
+
                         for (int i = 0; i < count; i++)
                         {
                             double val;
@@ -448,7 +452,9 @@ public void GetValues(DataTable table)
                 Dictionary<int, double> randomValues = new Dictionary<int, double>();
                 int count = EditorSettings.MaxSampleCount;
                 int max = table.Rows.Count;
-                Random rnd = new Random();
+
+                // Specified seed is required for consistently recreating the break values
+                Random rnd = new Random(9999);
                 for (int i = 0; i < count; i++)
                 {
                     double val;

diff --git a/Source/DotSpatial.Symbology/NaturalBreaks.cs b/Source/DotSpatial.Symbology/NaturalBreaks.cs
@@ -91,7 +91,7 @@ private void GetMatrices()
                 _lowerClassLimits[1, i] = 1;
                 _varianceCombinations[1, i] = 0;
 
-                // in the original implementation, 9999999 is used but since Javascript has `Infinity`, we use that.
+                // in the original implementation, 9999999 is used but since C# has `PositiveInfinity`, we use that.
                 for (j = 2; j < _values.Length + 1; j++)
                 {
                     _varianceCombinations[j, i] = double.PositiveInfinity;