Re #9682. Changed behavior of interpolation with one value

In the previous commit, I fixed the problem caused by having only one value in the interpolation table by return 0. On second thought, it makes more sense to assume a "constant interpolation" and return the one stored y-value for any x.
mantidproject · Jun 30, 2014 · 2e62762 · 2e62762
1 parent 167c634
commit 2e62762
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Showing 2 changed files with 11 additions and 4 deletions.
diff --git a/Code/Mantid/Framework/Kernel/src/Interpolation.cpp b/Code/Mantid/Framework/Kernel/src/Interpolation.cpp
@@ -60,11 +60,16 @@ namespace Kernel
   {
     size_t N = m_x.size();
 
-    if ( N < 2 )
+    if ( N == 0 )
     {
-      g_log.error() << "Need at least two values for interpolation. Return interpolation value zero.";
+      g_log.error() << "Need at least one value for interpolation. Return interpolation value zero.";
       return 0.0;
     }
+
+    if ( N == 1 )
+    {
+      return m_y[0];
+    }
 
     // check first if at is within the limits of interpolation interval
 

diff --git a/Code/Mantid/Framework/Kernel/test/InterpolationTest.h b/Code/Mantid/Framework/Kernel/test/InterpolationTest.h
@@ -201,9 +201,11 @@ class InterpolationTest : public CxxTest::TestSuite
         interpolationOne.addPoint(200, 2.0);
 
         for(size_t i = 0; i < m_tableXValues.size(); ++i) {
-            // When there are only one or two values in the interpolation, it returns 0.0
+            // When there are zero values in the interpolation, it returns 0.0
             checkValue(interpolationZero, m_tableXValues[i], 0.0, "zero interpolation values");
-            checkValue(interpolationOne, m_tableXValues[i], 0.0, "one interpolation value");
+
+            // With one value, it returns this one value for any x.
+            checkValue(interpolationOne, m_tableXValues[i], 2.0, "one interpolation value");
         }
     }