Refs #4313: Fix for repeated time values in ALD

addLogDerivative
mantidproject · Dec 12, 2011 · 04ead62 · 04ead62
1 parent b244242
commit 04ead62
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Showing 2 changed files with 41 additions and 12 deletions.
diff --git a/Code/Mantid/Framework/Algorithms/src/AddLogDerivative.cpp b/Code/Mantid/Framework/Algorithms/src/AddLogDerivative.cpp
@@ -1,14 +1,15 @@
 /*WIKI* 
 
-
-
 This algorithm performs a simple numerical derivative of the values in a sample log.
 
 The 1st order derivative is simply: dy = (y1-y0) / (t1-t0), which is placed in the log at t=(t0+t1)/2
 
-Higher order derivatives are obtained by performing the equation above N times. Since this is a simple numerical derivative, you can expect the result to quickly get noisy at higher derivatives.
-
+Higher order derivatives are obtained by performing the equation above N times.
+Since this is a simple numerical derivative, you can expect the result to quickly
+get noisy at higher derivatives.
 
+If any of the times in the logs are repeated, then those repeated time values will be skipped,
+and the output derivative log will have fewer points than the input.
 
 *WIKI*/
 #include "MantidAlgorithms/AddLogDerivative.h"
@@ -94,21 +95,31 @@ namespace Algorithms
     {
       dVal.clear();
       dTime.clear();
+      double t0 = times[0];
+      double y0 = values[0];
       for (size_t i=0; i<times.size()-1; i++)
       {
-        double y0 = values[i];
         double y1 = values[i+1];
-        double t0 = times[i];
         double t1 = times[i+1];
-        double dy = (y1-y0) / (t1-t0);
-        double t = (t0+t1)/2.0;
-        dVal.push_back( dy );
-        dTime.push_back( t );
+        if (t1 != t0)
+        {
+          // Avoid repeated time values giving infinite derivatives
+          double dy = (y1-y0) / (t1-t0);
+          double t = (t0+t1)/2.0;
+          dVal.push_back( dy );
+          dTime.push_back( t );
+          // For the next time interval
+          t0 = t1;
+          y0 = y1;
+        }
       }
       times = dTime;
       values = dVal;
     }
 
+    if (times.size() == 0)
+      throw std::runtime_error("Log " + input->name() + " did not have enough non-repeated time values to make this derivative.");
+
     // Convert time in sec to DateAndTime
     DateAndTime start = input->nthTime(0);
     std::vector<DateAndTime> timeFull;

diff --git a/Code/Mantid/Framework/Algorithms/test/AddLogDerivativeTest.h b/Code/Mantid/Framework/Algorithms/test/AddLogDerivativeTest.h
@@ -36,7 +36,8 @@ class AddLogDerivativeTest : public CxxTest::TestSuite
   }
 
   /** Perform test, return result */
-  TimeSeriesProperty<double> * do_test(int Derivative, bool willFail = false)
+  TimeSeriesProperty<double> * do_test(int Derivative, bool willFail = false,
+      bool addRepeatedTimes = false)
   {
     Workspace2D_sptr ws = WorkspaceCreationHelper::Create2DWorkspace(10, 10);
     AnalysisDataService::Instance().addOrReplace("Dummy", ws);
@@ -46,9 +47,15 @@ class AddLogDerivativeTest : public CxxTest::TestSuite
     TS_ASSERT( p->addValue("2007-11-30T16:17:10",2.00) );
     TS_ASSERT( p->addValue("2007-11-30T16:17:20",0.00) );
     TS_ASSERT( p->addValue("2007-11-30T16:17:30",5.00) );
+    if (addRepeatedTimes)
+    {
+      TS_ASSERT( p->addValue("2007-11-30T16:17:30",10.00) );
+      TS_ASSERT( p->addValue("2007-11-30T16:17:40",15.00) );
+      TS_ASSERT( p->addValue("2007-11-30T16:17:50",20.00) );
+    }
     ws->mutableRun().addProperty(p, true);
 
-    std::string NewLogName = "doubleProp_derived";
+    std::string NewLogName = "doubleProp_deriv";
 
     AddLogDerivative alg;
     TS_ASSERT_THROWS_NOTHING( alg.initialize() )
@@ -110,6 +117,17 @@ class AddLogDerivativeTest : public CxxTest::TestSuite
     TS_ASSERT_DELTA( p->nthValue(0), 0.01, 1e-5);
   }
 
+  /** Ticket #4313: Handled repeated time values in logs */
+  void test_exec_1stDerivative_repeatedValues()
+  {
+    TimeSeriesProperty<double> * p = do_test(1, false, true);
+    if (!p) return;
+    TS_ASSERT_EQUALS( p->size(), 5);
+    TS_ASSERT_EQUALS( p->nthTime(3).to_ISO8601_string(), "2007-11-30T16:17:35");
+    TS_ASSERT_DELTA( p->nthValue(3), 1.0, 1e-5);
+    TS_ASSERT_EQUALS( p->nthTime(4).to_ISO8601_string(), "2007-11-30T16:17:45");
+    TS_ASSERT_DELTA( p->nthValue(4), 0.5, 1e-5);
+  }
 
   void test_exec_failures()
   {