further fixes

Author: martamaja10

tree/dataframe/src/RDataFrame.cxx

@@ -1938,8 +1938,7 @@ tree->Draw("x", "y > 2");
    <td>
 ~~~{.cpp}
 ROOT::RDataFrame df("myTree", file);
-auto h = df.Filter("y > 2").Histo1D("x");
-h->Draw();
+df.Filter("y > 2").Histo1D("x")->Draw();
 ~~~
    </td>
 </tr>
@@ -1952,10 +1951,7 @@ tree->Draw("jet_eta", "weight*(event == 1)");
    </td>
    <td>
 ~~~{.cpp}
-df.Filter("event == 1").Histo1D("jet_eta", "weight");
-
-// or the fully compiled version:
-df.Filter([] (ULong64_t e) { return e == 1; }, {"event"}).Histo1D<RVec<float>>("jet_eta", "weight");
+df.Filter("event == 1").Histo1D("jet_eta", "weight")->Draw();
 ~~~
    </td>
 </tr>
@@ -1964,15 +1960,13 @@ df.Filter([] (ULong64_t e) { return e == 1; }, {"event"}).Histo1D<RVec<float>>("
 ~~~{cpp}
 // Draw a histogram using the method of the class that is being used. 
 tree->Draw("event.GetNtrack()");
-// note: this will not work in RDataFrame version
-// tree->Draw("GetNtrack()");
 
 ~~~
    </td>
    <td>
 ~~~{cpp}
 auto df1 = df.Define("NTrack","event.GetNtrack()");
-auto df2 = df1.Histo1D<int>("NTrack");
+df1.Histo1D("NTrack")->Draw();
 ~~~
    </td>
 </tr>
@@ -1986,22 +1980,21 @@ tree->Draw("fNtrack","fEvtHdr.fEvtNum%10 == 0");
    <td>
 ~~~{cpp}
 // Use the Filter operation together with the special RDF column: `rdfentry_`
-auto histo = df.Filter("rdfentry_ % 10 == 0").Histo1D<int>("fNtrack");
-histo->Draw();
+df.Filter("rdfentry_ % 10 == 0").Histo1D("fNtrack")->Draw();
 ~~~
    </td>
 </tr>
 <tr>
    <td>
 ~~~{cpp}
 // object selection: for each event, fill histogram with array of selected pts
-tree->Draw('Muon_pt', 'Muon_pt > 100')
+tree->Draw('Muon_pt', 'Muon_pt > 100');
 ~~~
    </td>
    <td>
 ~~~{cpp}
 // with RDF, arrays are read as ROOT::VecOps::RVec objects
-df.Define("good_pt", "Muon_pt[Muon_pt > 100]").Histo1D<float>("good_pt");
+df.Define("good_pt", "Muon_pt[Muon_pt > 100]").Histo1D("good_pt")->Draw();
 ~~~
    </td>
 </tr>
@@ -2021,14 +2014,8 @@ TH1F *hnew = (TH1F*)gPad->GetPrimitive("hnew");
    </td>
    <td>
 ~~~{cpp}
-// Save the histogram to a file
-TFile f("myhistos.root","new");
-auto hist = df.Filter("y>0").Histo1D<float>({"myhisto","myhisto",10, 0, 10},"x");
-f.WriteTObject(hist.GetPtr());
-
-// Retrieve the histogram
-TFile f("myhistos.root");
-TH1D *h = (TH1D*)f.Get("myhisto");
+// We pass histogram constructor arguments to the Histo1D operation, to easily give the histogram a name
+auto hist = df.Filter("y>0").Histo1D({"hnew","hnew",10, 0, 10},"x");
 ~~~
    </td>
 </tr>
@@ -2044,11 +2031,12 @@ tree->Draw("z:y:x","","prof");
    </td>
    <td>
 ~~~{cpp}
+
 // Draw a 1D Profile histogram
-auto profile1D = df.Profile1D<int, float>({"profName", "profTitle", 10, 0, 10}, "x", "y");
+auto profile1D = df.Profile1D("x", "y");
 
 // Draw a 2D Profile histogram
-auto profile2D = df.Profile2D<int, float, double>({"profName", "profTitle", 10u, 0, 10, 10, 0, 10}, "x", "y", "z");
+auto profile2D = df.Profile2D("x", "y", "z");
 ~~~
    </td>
 </tr>
@@ -2077,45 +2065,23 @@ tree->Draw("vec_list.X()");
    </td>
    <td>
 ~~~{cpp}
-auto getX = [](vector< ROOT::Math::DisplacementVector3D> &v){RVec<double> out; for( auto p: v) out.push_back(p.X()); return out;};
-auto histo = df.Define("X",getX,{"vec_list"}).Histo1D<double>("x");
+auto histo = df.Define("x", R"(ROOT::RVecD out; for(const auto &el: vec_list) out.push_back(el.X()); return out;)").Histo1D("x");
 histo->Draw();
 ~~~
    </td>
 </tr>
 <tr>
    <td>
 ~~~{cpp}
-// Draw 2D arrays
-tree->Draw("fMatrix");
-tree->Draw("fMatrix[ ][ ]");
-tree->Draw("fMatrix[2][2]");
-tree->Draw("fMatrix[][0]"); 
-// and so on: 
-// fMatrix[1][0], fMatrix[2][0], fMatrix[3][0], ... , fMatrix[n][0]
-
-~~~
-   </td>
-   <td>
-~~~{cpp}
-Reading multi-dimensional arrays is not supported in RDF. 
-GH issue exists. If such feature is needed, please add a comment: "https://github.com/root-project/root/issues/15068"
-~~~
-   </td>
-</tr>
-<tr>
-   <td>
-~~~{cpp}
-// Count number of entries in a specific dataset branch
-tree->Draw("pt"); 
-TH1* myH {static_cast<TH1*>(gPad->GetPrimitive(\"htemp\"))}; 
-myH->GetEntries();
+// Count number of entries in a specific dataset branch in case this branch has fewer entries than the full dataset
+tree->Draw("pt>>histo");
+TH1D histo = (TH1D)gDirectory->Get("histo");
+histo->GetEntries();
 ~~~
    </td>
    <td>
 ~~~{cpp}
-auto df = ROOT::RDataFrame("tree", "file.root");
-df.Histo1D<double>("pt")->GetEntries();
+df.Histo1D("pt")->GetEntries();
 ~~~
    </td>
 </tr>