Refs #8550. Use detector IDs for grouping instead of spectra indices.

This is consistent to how GroupDetectors works and how information
is stored in the files.

Code/Mantid/Framework/Algorithms/src/MuonGroupDetectors.cpp

@@ -104,17 +104,22 @@ namespace Algorithms
     // Compile the groups
     for ( auto rowIt = nonEmptyRows.begin(); rowIt != nonEmptyRows.end(); ++rowIt )
     {    
-      // Not "detectors" as such, but workspace indices. For Muons there is only one detector for
-      // workspace index in the data before grouping.
-      std::vector<int>& detectors = table->cell< std::vector<int> >(*rowIt, 0);
-
       // Group index in the output workspace
       size_t groupIndex = static_cast<size_t>( std::distance(nonEmptyRows.begin(), rowIt) );
 
+      std::vector<int>& detectorIDs = table->cell< std::vector<int> >(*rowIt, 0);
+
+      // Recieve detector IDs, but need workspace indices to group, so convert
+      std::vector<size_t> wsIndices;
+      inWS->getIndicesFromDetectorIDs(detectorIDs, wsIndices);
+
+      if ( wsIndices.size() != detectorIDs.size() )
+        throw std::invalid_argument("Some of the detector IDs were not found");
+
       // We will be setting them anew
       outWS->getSpectrum(groupIndex)->clearDetectorIDs();
 
-      for(auto detIt = detectors.begin(); detIt != detectors.end(); detIt++)
+      for(auto detIt = wsIndices.begin(); detIt != wsIndices.end(); detIt++)
       {
         for( size_t i = 0; i < inWS->blocksize(); ++i )
         {
@@ -131,7 +136,7 @@ namespace Algorithms
       }
 
       // Using the first detector X values
-      outWS->dataX(groupIndex) = inWS->dataX(detectors.front());
+      outWS->dataX(groupIndex) = inWS->dataX(wsIndices.front());
 
       outWS->getSpectrum(groupIndex)->setSpectrumNo( static_cast<specid_t>(groupIndex + 1) );
     }

Code/Mantid/Framework/Algorithms/test/MuonGroupDetectorsTest.h

@@ -38,6 +38,9 @@ class MuonGroupDetectorsTest : public CxxTest::TestSuite
 
     MatrixWorkspace_sptr inWS = WorkspaceCreationHelper::Create2DWorkspace123(5,3);
 
+    for ( size_t i = 0; i < inWS->getNumberHistograms(); ++i )
+      inWS->getSpectrum(i)->setDetectorID( static_cast<detid_t>(i + 1) ); // To be consistent with how LoadMuonNexus works
+
     TableWorkspace_sptr grouping = createDetectorGroupingTable(); 
 
     MuonGroupDetectors alg;
@@ -71,11 +74,11 @@ class MuonGroupDetectorsTest : public CxxTest::TestSuite
       TS_ASSERT_EQUALS( ws->getSpectrum(1)->getSpectrumNo(), 2);
 
       std::set<detid_t> d1;
-      d1.insert(0); d1.insert(1);
+      d1.insert(1); d1.insert(2);
       TS_ASSERT_EQUALS( ws->getSpectrum(0)->getDetectorIDs(), d1 );
 
       std::set<detid_t> d2;
-      d2.insert(2); d2.insert(3); d2.insert(4);
+      d2.insert(3); d2.insert(4); d2.insert(5);
       TS_ASSERT_EQUALS( ws->getSpectrum(1)->getDetectorIDs(), d2 );
     }
 
@@ -92,12 +95,12 @@ class MuonGroupDetectorsTest : public CxxTest::TestSuite
     t->addColumn("vector_int", "Detectors");
 
     std::vector<int> group1;
-    group1.push_back(0); group1.push_back(1);
+    group1.push_back(1); group1.push_back(2);
     TableRow row1 = t->appendRow();
     row1 << group1;
 
     std::vector<int> group2;
-    group2.push_back(2); group2.push_back(3); group2.push_back(4);
+    group2.push_back(3); group2.push_back(4); group2.push_back(5);
     TableRow row2 = t->appendRow();
     row2 << group2;
 

Code/Mantid/Framework/DataHandling/src/LoadMuonNexus1.cpp

@@ -635,7 +635,9 @@ namespace Mantid
 
       for ( auto it = begin; it != end; ++it )
       {
-        grouping[*it].push_back( static_cast<int>( std::distance(begin,it) ) );
+        // Add detector ID to the list of group detectors. Detector ID is always 
+        // spectra index + 1
+        grouping[*it].push_back( static_cast<int>( std::distance(begin,it) ) + 1 );
       }
 
       for ( auto it = grouping.begin(); it != grouping.end(); ++it )

Code/Mantid/Framework/DataHandling/test/LoadMuonNexus1Test.h

@@ -532,11 +532,11 @@ class LoadMuonNexus1Test : public CxxTest::TestSuite
       TS_ASSERT_EQUALS( e1.size(), 16);
       TS_ASSERT_EQUALS( e2.size(), 16);
 
-      TS_ASSERT_EQUALS( e1[0], 0 );
-      TS_ASSERT_EQUALS( e1[15], 15);
+      TS_ASSERT_EQUALS( e1[0], 1 );
+      TS_ASSERT_EQUALS( e1[15], 16);
 
-      TS_ASSERT_EQUALS( e2[0], 16 );
-      TS_ASSERT_EQUALS( e2[15], 31 );
+      TS_ASSERT_EQUALS( e2[0], 17 );
+      TS_ASSERT_EQUALS( e2[15], 32 );
     }
 
     AnalysisDataService::Instance().remove(outWSName);
@@ -586,11 +586,11 @@ class LoadMuonNexus1Test : public CxxTest::TestSuite
         TS_ASSERT_EQUALS( e1.size(), 32);
         TS_ASSERT_EQUALS( e2.size(), 32);
 
-        TS_ASSERT_EQUALS( e1[0], 32 );
-        TS_ASSERT_EQUALS( e1[31], 63 );
+        TS_ASSERT_EQUALS( e1[0], 33 );
+        TS_ASSERT_EQUALS( e1[31], 64 );
 
-        TS_ASSERT_EQUALS( e2[0], 0 );
-        TS_ASSERT_EQUALS( e2[31], 31 );
+        TS_ASSERT_EQUALS( e2[0], 1 );
+        TS_ASSERT_EQUALS( e2[31], 32 );
       }
 
       TableWorkspace_sptr table2 = boost::dynamic_pointer_cast<TableWorkspace>( detectorGrouping->getItem(1) );
@@ -608,11 +608,11 @@ class LoadMuonNexus1Test : public CxxTest::TestSuite
         TS_ASSERT_EQUALS( e1.size(), 32);
         TS_ASSERT_EQUALS( e2.size(), 32);
 
-        TS_ASSERT_EQUALS( e1[0], 32 );
-        TS_ASSERT_EQUALS( e1[31], 63 );
+        TS_ASSERT_EQUALS( e1[0], 33 );
+        TS_ASSERT_EQUALS( e1[31], 64 );
 
-        TS_ASSERT_EQUALS( e2[0], 0 );
-        TS_ASSERT_EQUALS( e2[31], 31);
+        TS_ASSERT_EQUALS( e2[0], 1 );
+        TS_ASSERT_EQUALS( e2[31], 32);
 
       }
     }