From c48e2be20b34844d23a213c9284fc8802887efe6 Mon Sep 17 00:00:00 2001
From: Andrew Zhen Ning Yong <andrew.yong@ed.ac.uk>
Date: Thu, 20 May 2021 11:49:03 +0100
Subject: [PATCH] Added feature to reject fit if 25% of sample fits are bad
 (with chi2perdof > 2 or is a NaN)

---
 lib/Statistics/XYSampleData.cpp | 16 ++++++++++++++--
 lib/Statistics/XYSampleData.hpp |  1 +
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/Statistics/XYSampleData.cpp b/lib/Statistics/XYSampleData.cpp
index 19342c9..b336b62 100644
--- a/lib/Statistics/XYSampleData.cpp
+++ b/lib/Statistics/XYSampleData.cpp
@@ -244,9 +244,15 @@ void XYSampleData::checkChi2PerDof(double Chi2PerDof)
     if(Chi2PerDof >= 2 or Chi2PerDof < 0 or isnan(Chi2PerDof)) 
     {
         goodFit_ = false;
-        cerr << "chi2PerDof = " << Chi2PerDof << ". Aborting fit now." << endl;
     }
+}
 
+void XYSampleData::checkChi2PerDof(double Chi2PerDof, unsigned int &counter)
+{
+    if(Chi2PerDof >= 2 or Chi2PerDof < 0 or isnan(Chi2PerDof)) 
+    {
+        counter++;
+    }
 }
 
 // get total fit variance matrix and its pseudo-inverse ////////////////////////
@@ -308,6 +314,7 @@ SampleFitResult XYSampleData::fit(std::vector<Minimizer *> &minimizer,
     result.chi2_.resize(nSample_);
     result.model_.resize(v.size());
     double chi2PerDof;
+    unsigned int badSampleFits = 0;
     goodFit_ = true;
     FOR_STAT_ARRAY(result, s)
     {
@@ -325,7 +332,7 @@ SampleFitResult XYSampleData::fit(std::vector<Minimizer *> &minimizer,
             {
                 sampleResult = data_.fit(*(minimizer.back()), initCopy, v);
                 chi2PerDof   = sampleResult.getChi2PerDof();
-                checkChi2PerDof(chi2PerDof);
+                checkChi2PerDof(chi2PerDof, badSampleFits);
             }
             result[s]       = sampleResult;
             result.chi2_[s] = sampleResult.getChi2();
@@ -335,6 +342,11 @@ SampleFitResult XYSampleData::fit(std::vector<Minimizer *> &minimizer,
                 result.model_[j][s] = sampleResult.getModel(j);
 
             }
+            if(badSampleFits > 0.25*nSample_) 
+            {
+                goodFit_ = false;
+                cerr << "At least " << 0.25*nSample_ << " of the sample fits have bad chi2/dof. Aborting fit." << endl;
+            }
         }
     }
     result.nPar_    = sampleResult.getNPar();
diff --git a/lib/Statistics/XYSampleData.hpp b/lib/Statistics/XYSampleData.hpp
index a66c9dd..c5c61b5 100644
--- a/lib/Statistics/XYSampleData.hpp
+++ b/lib/Statistics/XYSampleData.hpp
@@ -93,6 +93,7 @@ public:
     DVec               getYError(const Index j);
     bool               checkFit(); // check fit candidate based on chi2PerDof
     void               checkChi2PerDof(double Chi2PerDof);
+    void               checkChi2PerDof(double Chi2PerDof, unsigned int &counter);
     // get total fit variance matrix and its pseudo-inverse
     const DMat & getFitVarMat(void);
     const DMat & getFitVarMatPInv(void);