Division of pad

[Gursharan_singh]

#include "TFile.h"
#include "TH1F.h"
#include "TCanvas.h"
#include "TKey.h"
#include <iostream>
#include "TLegend.h"
#include "TPaveStats.h"
#include "TStyle.h"

void DrawOverlayHistograms(const char* file1, const char* file2) {
    // Open the ROOT files containing the histograms
    TFile *fileABC = TFile::Open(file1);
    TFile *fileABCMC = TFile::Open(file2);

    if (!fileABC || !fileABCMC) {
        std::cerr << "Error opening input files!" << std::endl;
        return;
    }

    TList *keysABC = fileABC->GetListOfKeys();
    TIter nextABC(keysABC);
    TKey *keyABC;

    // Loop through the histograms in file1
    while ((keyABC = (TKey*)nextABC())) {
        TObject *objABC = keyABC->ReadObj();
        if (objABC->IsA()->InheritsFrom(TH1::Class())) {
            TH1F *histogramABC = (TH1F*)objABC;
            const char* histName = histogramABC->GetName();

            // Get the corresponding histogram from file2
            TH1F *histogramABCMC = (TH1F*)fileABCMC->Get(Form("%s_mc", histName));
            
            const char* histName2 = histogramABCMC->GetName();

            if (histogramABCMC && histogramABCMC->InheritsFrom(TH1::Class())) {
                std::cout << "Histogram found: " << histName << std::endl;
                
                histogramABCMC->Scale(histogramABC->GetEntries() / histogramABCMC->GetEntries());

                // Set fill color and style for histogramABCMC
                const char* title = Form("%s vs %s", histName,histName2);
		histogramABCMC->SetTitle(title);
		histogramABC->SetTitle("");

                histogramABCMC->SetFillColor(kYellow);
                histogramABCMC->SetFillStyle(3001); // Pattern style for filling
                histogramABC->SetTitle("");
                histogramABC->SetMarkerColor(kRed); // Set marker color to red
		histogramABC->SetMarkerStyle(20);   // Define the marker style (adjust as needed)
		histogramABC->SetMarkerSize(1.2); 
		const char* xAxisLabel = Form("%s -->", histName);
		histogramABCMC->GetXaxis()->SetTitle(xAxisLabel);
		histogramABCMC->GetYaxis()->SetTitle("events -->");
		histogramABCMC->GetXaxis()->CenterTitle();
		histogramABCMC->GetYaxis()->CenterTitle();
		
		TPad* pad;
                // Create and draw the canvas
                TCanvas *canvas = new TCanvas("canvas", "Overlay Histograms", 800, 600);
                TPad *upperPad = new TPad("upperPad", "Upper Pad", 0, 0.3, 1, 1);
                upperPad->SetBottomMargin(0.2); // Upper and lower plot are joined
                upperPad->SetGridx(); // Vertical grid
                
                upperPad->SetBottomMargin(0); // Set the bottom margin of the upper pad to zero
		//upperPad->SetBottomMargin(0); // Set the bottom margin of the upper pad to zero
		upperPad->SetTopMargin(0.1); // Adjust the top margin of t
		upperPad->SetGridx();
		upperPad->Draw();
                upperPad->cd();
                canvas->SetFillColor(kWhite); // Set canvas background color
                
                		
		gStyle->SetOptStat("nemr");
		pad = (TPad*)canvas->cd();
		histogramABCMC->Draw("HIST");
		
		gPad->Update();
		auto stat = dynamic_cast<TPaveStats*>(histogramABCMC->FindObject("stats"));
		if (stat) {
		std::cout << " X1NDC: " << stat->GetX1NDC() << " X2NDC: " << stat->GetX2NDC() << std::endl;
		stat->SetX1NDC(0.8); stat->SetX2NDC(.95);
		stat->SetY1NDC(0.6); stat->SetY2NDC(0.75);
		stat->Draw();
		}

               // histogramABCMC->Draw("HIST");
                histogramABC->Draw("SAMES");
                
	    auto legend = new TLegend(0.79, 0.5, 0.92, 0.6);

	   legend->SetHeader("MC vs REAL","C"); // option "C" allows to center the header
	   legend->AddEntry(histogramABCMC ,"MC_Histogram","f");
	   legend->AddEntry(histogramABC,"Data_Histogram");
	   legend->Draw();
	   
	  
          canvas->cd();
	TPad *lowerPad = new TPad("lowerPad", "Lower Pad", 0, 0, 1, 0.3);
	lowerPad->SetTopMargin(0);
	lowerPad->SetBottomMargin(0.2);
	lowerPad->SetGridx(); // Vertical grid
	lowerPad->SetTopMargin(0); // Set the top margin of the lower pad to zero
	//lowerPad->SetBottomMargin(0.2); 
	lowerPad->Draw();
	lowerPad->cd();

	// Calculate and draw the ratio plot
	TH1F *ratioHistogram = (TH1F*)histogramABC->Clone();
	ratioHistogram->Divide(histogramABCMC);
	ratioHistogram->GetXaxis()->SetLabelSize(0.08); // Adjust the value as needed

	// Increase the font size of the Y axis
	ratioHistogram->GetYaxis()->SetLabelSize(0.08);
	ratioHistogram->SetMarkerStyle(20);
	ratioHistogram->Draw("ep");

	// Adjust the TPaveStats size and font for the lower pad
	gPad->Update();
	auto statLower = dynamic_cast<TPaveStats*>(ratioHistogram->FindObject("stats"));
	if (statLower) {
	    statLower->SetX1NDC(0.8); // Adjust the X1NDC to move the stats box to the left
	    statLower->SetX2NDC(0.9); // Adjust the X2NDC to make the stats box wider
	    statLower->SetTextSize(0.06); // Increase the text size within the stats box
	  //  statLower->SetTextFont(43); // Set the font (43 is Times New Roman, you can change it)
	   statLower->SetY2NDC(1);
	   statLower->SetY1NDC(.5);
	    statLower->Draw();
	}



                canvas->SaveAs(Form("Overlay_%s.png", histName)); // Save canvas as an image
                delete canvas;
            } else {
                std::cerr << "Histogram not found: " << histName << std::endl;
            }
        }
    }

    // Close the input files
    fileABC->Close();
    fileABCMC->Close();
}



int main() {
    const char* file1 = "Data_Run2022.root"; // Path to the first ROOT file
    const char* file2 = "MC_Run2022.root";   // Path to the second ROOT file

    DrawOverlayHistograms(file1, file2);

    return 0;
}

here my lower pad is actually overlaping the top pad content , could anyone please check where is the mistake

[couet]

I do not have your data files. I cannot run your macro.