Added title to each axis of histograms. Default is empty

GaudiCommonSvc/src/HistogramPersistencySvc/RootHistogramSink.cpp

@@ -32,12 +32,14 @@ namespace {
     unsigned int nBins;
     double minValue;
     double maxValue;
+    std::string title;
   };
   
   Axis toAxis( nlohmann::json& jAxis ) {
     return { jAxis.at("nBins").get<unsigned int>(),
              jAxis.at("minValue").get<double>(),
-             jAxis.at("maxValue").get<double>() };
+             jAxis.at("maxValue").get<double>(),
+             ";" + jAxis.at("title").get<std::string>() }; // ";" to prepare concatenations of titles
   }
 
   template <typename Traits, std::size_t... index>
@@ -49,6 +51,8 @@ namespace {
     auto axis     = std::array{toAxis( jsonAxis[index] )...};
     auto weights  = j.at( "bins" ).get<std::vector<typename Traits::WeightType>>();
     auto title = j.at("title").get<std::string>();
+    // weird way ROOT has to give titles to axis
+    title += (axis[index].title + ...);
     // compute total number of bins, multiplying bins per axis
     auto totNBins = ((axis[index].nBins+2) * ...);
     assert(weights.size() == totNBins);

GaudiExamples/src/Histograms/CounterHistos.cpp

@@ -141,11 +141,11 @@ namespace Gaudi {
 
         // "default" case, that is bins containing doubles and atomic
         mutable Gaudi::Accumulators::Histogram<1> m_gauss{
-                                                                    this, "Gauss", "Gaussian mean=0, sigma=1, atomic", {100, -5, 5}};
+                                                          this, "Gauss", "Gaussian mean=0, sigma=1, atomic", {100, -5, 5, "X"}};
         mutable Gaudi::Accumulators::Histogram<2> m_gaussVflat{
-                                                                         this, "GaussFlat", "Gaussian V Flat, atomic", {{50, -5, 5}, {50, -5, 5}}};
+                                                               this, "GaussFlat", "Gaussian V Flat, atomic", {{50, -5, 5, "X"}, {50, -5, 5, "Y"}}};
         mutable Gaudi::Accumulators::Histogram<3> m_gaussVflatVgauss{
-                                                                               this, "GaussFlatGauss", "Gaussian V Flat V Gaussian, atomic", {{10, -5, 5}, {10, -5, 5}, {10, -5, 5}}};
+                                                                     this, "GaussFlatGauss", "Gaussian V Flat V Gaussian, atomic", {{10, -5, 5, "X"}, {10, -5, 5, "Y"}, {10, -5, 5, "Z"}}};
 
         // non atomic versions
         mutable Gaudi::Accumulators::Histogram<1, Gaudi::Accumulators::atomicity::none> m_gauss_noato{

GaudiKernel/Gaudi/Accumulators/Histogram.h

@@ -113,12 +113,14 @@ namespace Gaudi::Accumulators {
    */
   template <typename Arithmetic>
   struct Axis {
-    Axis( unsigned int _nBins, Arithmetic _minValue, Arithmetic _maxValue )
-        : nBins( _nBins ), minValue( _minValue ), maxValue( _maxValue ), ratio( _nBins / ( _maxValue - _minValue ) ){};
+    Axis( unsigned int _nBins, Arithmetic _minValue, Arithmetic _maxValue, const std::string& _title="" )
+      : nBins( _nBins ), minValue( _minValue ), maxValue( _maxValue ), title(_title), ratio( _nBins / ( _maxValue - _minValue ) ){};
     /// number of bins for this Axis
     unsigned int nBins;
     /// min and max values on this axis
     Arithmetic minValue, maxValue;
+    /// title of this axis
+    std::string title;
     /**
      * precomputed ratio to convert a value into bin number
      * equal to nBins/(maxValue-minValue)
@@ -129,7 +131,7 @@ namespace Gaudi::Accumulators {
   /// automatic conversion of the Axis type to json
   template <typename Arithmetic>
   void to_json(nlohmann::json& j, const Axis<Arithmetic>& axis) {
-    j = nlohmann::json{{"nBins", axis.nBins}, {"minValue", axis.minValue}, {"maxValue", axis.maxValue}};
+    j = nlohmann::json{{"nBins", axis.nBins}, {"minValue", axis.minValue}, {"maxValue", axis.maxValue}, {"title", axis.title}};
   }
 
   /// small class used as InputType for regular Histograms
@@ -322,7 +324,7 @@ namespace Gaudi::Accumulators {
    * All these types have the same fields, namely :
    *   dimension(integer), title(string), empty(bool), nEntries(integer), axis(array), bins(array)
    * where :
-   *     + axis is an array of triplets, one per dimension, with content (nBins(integer), minValue(number), maxValue(number))
+   *     + axis is an array of tuples, one per dimension, with content (nBins(integer), minValue(number), maxValue(number), title(string))
    *     + bins is an array of values. The length of the array is the product of (nBins+2) for all axis
    *       the +2 is because the bin 0 is the one for values below minValue and bin nBins+1 is the one for values above maxValue
    *       bins are stored row first, so we iterate first on highest dimension