Implement rwp calculator. Refs #6746.

Code/Mantid/Framework/Kernel/inc/MantidKernel/Statistics.h

@@ -62,6 +62,8 @@ namespace Mantid
     /// Return the modified Z score values for a dataset
     template<typename TYPE>
     std::vector<double> getModifiedZscore(const std::vector<TYPE>& data, const bool sorted=false);
+    /// Return the R-factors (Rwp) of a diffraction pattern data
+    double getRFactor(const std::vector<double>& obsI, const std::vector<double>& calI, const std::vector<double>& obsE);
   
   } // namespace Kernel
 } // namespace Mantid

Code/Mantid/Framework/Kernel/src/Statistics.cpp

@@ -7,6 +7,8 @@
 #include <cmath>
 #include <numeric>
 #include <string>
+#include <stdexcept>
+#include <sstream>
 
 namespace Mantid
 {
@@ -214,6 +216,43 @@ namespace Mantid
       return getNanStatistics();
     }
 
+    /** Return the Rwp of a diffraction pattern data
+      * @param obsY :: array of observed intensity values
+      * @param calY :: array of calculated intensity values;
+      *
+      */
+    double getRFactor(const std::vector<double>& obsI, const std::vector<double>& calI, const std::vector<double>& obsE)
+    {
+      // 1. Check
+      if (obsI.size() != calI.size() || obsI.size() != obsE.size())
+      {
+        std::stringstream errss;
+        errss << "GetRFactor() Input Error!  Observed Intensity, Calculated Intensity and Observed Error have different number of elements.";
+        throw std::runtime_error(errss.str());
+      }
+
+      double sumnom = 0;
+      double sumdenom = 0;
+
+      size_t numpts = obsI.size();
+      for (size_t i = 0; i < numpts; ++i)
+      {
+        double cal_i = calI[i];
+        double obs_i = obsI[i];
+        double sigma = obsE[i];
+        double weight = 1.0/(sigma*sigma);
+        double diff = obs_i - cal_i;
+
+        sumnom += weight*diff*diff;
+        sumdenom += weight*obs_i*obs_i;
+      }
+
+      double rwp = std::sqrt(sumnom/sumdenom);
+
+      return rwp;
+    }
+
+
     // -------------------------- Macro to instantiation concrete types --------------------------------
 #define INSTANTIATE(TYPE) \
     template MANTID_KERNEL_DLL Statistics getStatistics<TYPE> (const vector<TYPE> &, const bool); \

Code/Mantid/Framework/Kernel/test/StatisticsTest.h

@@ -115,6 +115,75 @@ public:
     TS_ASSERT(my_isnan(stats.maximum));
     TS_ASSERT(my_isnan(stats.median));
   }
+
+  /** Test function to calculate Rwp
+    */
+  void testRwp()
+  {
+    vector<double> obsY(4);
+    vector<double> calY(4);
+    vector<double> obsE(4);
+
+    obsY[0] = 1.0;
+    calY[0] = 1.1;
+    obsE[0] = 1.0;
+
+    obsY[1] = 2.0;
+    calY[1] = 2.1;
+    obsE[1] = 1.2;
+
+    obsY[2] = 3.0;
+    calY[2] = 3.5;
+    obsE[2] = 1.4;
+
+    obsY[3] = 1.0;
+    calY[3] = 1.3;
+    obsE[3] = 1.0;
+
+    double rwp = getRFactor(obsY, calY, obsE);
+
+    TS_ASSERT_DELTA(rwp, 0.1582, 0.0001);
+
+  }
 };
 
 #endif // STATISTICSTEST_H_
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