Merge pull request #13069 from mantidproject/13056_Fix_X_label_after_FFT

Fix X label after FFT transformation

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

@@ -3,6 +3,7 @@
 //----------------------------------------------------------------------
 #include "MantidAlgorithms/FFT.h"
 #include "MantidKernel/UnitFactory.h"
+#include "MantidKernel/UnitLabelTypes.h"
 #include "MantidAPI/TextAxis.h"
 
 #include <boost/shared_array.hpp>
@@ -127,25 +128,41 @@ void FFT::exec() {
   MatrixWorkspace_sptr outWS =
       WorkspaceFactory::Instance().create(inWS, nOut, xSize, ySize);
 
-  bool isEnergyMeV = false;
-  if (inWS->getAxis(0)->unit() &&
-      (inWS->getAxis(0)->unit()->caption() == "Energy" ||
-       inWS->getAxis(0)->unit()->caption() == "Energy transfer") &&
-      inWS->getAxis(0)->unit()->label() == "meV") {
+  double df = 1.0 / (dx * ySize);
+
+  // Output label
+  outWS->getAxis(0)->unit() = UnitFactory::Instance().create("Label");
+
+  auto inputUnit = inWS->getAxis(0)->unit();
+  if (inputUnit) {
+
     boost::shared_ptr<Kernel::Units::Label> lblUnit =
         boost::dynamic_pointer_cast<Kernel::Units::Label>(
             UnitFactory::Instance().create("Label"));
     if (lblUnit) {
-      lblUnit->setLabel("Time", "ns");
+
+      if ((inputUnit->caption() == "Energy" ||
+           inputUnit->caption() == "Energy transfer") &&
+          inputUnit->label() == "meV") {
+        lblUnit->setLabel("Time", "ns");
+        df /= 2.418e2;
+      } else if (inputUnit->caption() == "Time" && inputUnit->label() == "s") {
+        lblUnit->setLabel("Frequency", "Hz");
+      } else if (inputUnit->caption() == "Frequency" && inputUnit->label() == "Hz") {
+        lblUnit->setLabel("Time", "s");
+      } else if (inputUnit->caption() == "Time" && inputUnit->label() == "microsecond") {
+        lblUnit->setLabel("Frequency", "MHz");
+      } else if (inputUnit->caption() == "Frequency" && inputUnit->label() == "MHz") {
+        lblUnit->setLabel("Time", Units::Symbol::Microsecond);
+      } else if (inputUnit->caption() == "d-Spacing" && inputUnit->label() == "Angstrom") {
+        lblUnit->setLabel("q", Units::Symbol::InverseAngstrom);
+      } else if (inputUnit->caption() == "q" && inputUnit->label() == "Angstrom^-1") {
+        lblUnit->setLabel("d-Spacing", Units::Symbol::Angstrom);
+      }
+
       outWS->getAxis(0)->unit() = lblUnit;
     }
-    isEnergyMeV = true;
-  } else
-    outWS->getAxis(0)->unit() = UnitFactory::Instance().create("Label");
-
-  double df = 1.0 / (dx * ySize);
-  if (isEnergyMeV)
-    df /= 2.418e2;
+  }
 
   // centerShift == true means that the zero on the x axis is assumed to be in
   // the data centre

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

@@ -9,6 +9,7 @@
 #include "MantidAPI/FrameworkManager.h"
 #include "MantidAPI/MatrixWorkspace.h"
 #include "MantidDataObjects/Workspace2D.h"
+#include "MantidKernel/UnitFactory.h"
 
 using namespace Mantid;
 using namespace Mantid::API;
@@ -382,6 +383,10 @@ public:
     MatrixWorkspace_sptr fWS = boost::dynamic_pointer_cast<MatrixWorkspace>
       (AnalysisDataService::Instance().retrieve("FFT_out"));
 
+    // Test the output label
+    TS_ASSERT_EQUALS(fWS->getAxis(0)->unit()->caption(), "Quantity");
+    TS_ASSERT_EQUALS(fWS->getAxis(0)->unit()->label(), "");
+
     const MantidVec& X = fWS->readX(0);
     const MantidVec& Yr = fWS->readY(0);
     const MantidVec& Yi = fWS->readY(1);
@@ -408,6 +413,49 @@ public:
     FrameworkManager::Instance().deleteWorkspace("FFT_out");
   }
 
+  void testUnitsEnergy() {
+
+    const int N = 100;
+    const double XX = dX * N;
+    double dx = 1/(XX);
+
+    MatrixWorkspace_sptr WS = createWS(N,1,"even_hist");
+
+    // Set a label
+    WS->getAxis(0)->unit() = Mantid::Kernel::UnitFactory::Instance().create("Energy");
+
+    IAlgorithm* fft = Mantid::API::FrameworkManager::Instance().createAlgorithm("FFT");
+    fft->initialize();
+    fft->setPropertyValue("InputWorkspace","FFT_WS_even_hist");
+    fft->setPropertyValue("OutputWorkspace","FFT_out");
+    fft->setPropertyValue("Real","0");
+    fft->execute();
+
+    MatrixWorkspace_sptr fWS = boost::dynamic_pointer_cast<MatrixWorkspace>
+      (AnalysisDataService::Instance().retrieve("FFT_out"));
+
+    // Test X values
+    // When the input unit is 'Energy' in 'meV'
+    // there is a factor of 1/2.418e2 in X
+    const MantidVec& X = fWS->readX(0);
+
+    const MantidVec::const_iterator it = std::find(X.begin(),X.end(),0.);
+    int i0 = static_cast<int>(it - X.begin());
+
+    for (int i = 0; i < N / 4; i++) {
+      int j = i0 + i;
+      double x = X[j];
+      TS_ASSERT_DELTA(x, dx * i /2.418e2, 0.00001);
+    }
+
+    // Test the output label
+    TS_ASSERT_EQUALS(fWS->getAxis(0)->unit()->caption(),"Time");
+    TS_ASSERT_EQUALS(fWS->getAxis(0)->unit()->label(),"ns");
+
+    FrameworkManager::Instance().deleteWorkspace("FFT_WS_even_hist");
+    FrameworkManager::Instance().deleteWorkspace("FFT_out");
+  }
+
 private:
 
   MatrixWorkspace_sptr createWS(int n,int dn,const std::string& name)