Multigraph - empty plot

[faca87]

Hello, I wrote this macro to plot a multigraph reading data from a .txt file
mulgr.cpp (1.8 KB)

This is the data file
data.txt (183 Bytes)

gr1 must plot the data of second culumn in function of first one of data file
gr2 must plot the data of third culomn in function of the first one

but when I run the macro, I don’t get the plots, but just the legend and the text bloxes…

---

Please read tips for efficient and successful posting and posting code

_ROOT Version:6.25.01
_Platform:Windows10
_Compiler:Visual Studio 2019 Developer Command Prompt v16.9.2

---

[couet]

   mg->Draw("ALP");

[faca87]

Hello @couet thank you, it worked and now I get correctly the plot

Now I need to add a second Cartesian plane under the first one to plot the difference between the 2 graphs…
ie. I need something like this

on the top I’ve the plot of values and on the bottom I have a smaller plot for the difference then I added

auto rp1 = new TRatioPlot(gr1,gr2);
   rp1->Draw();
   rp1->GetLowerRefYaxis()->SetTitle("ratio");
   rp1->GetUpperRefYaxis()->SetTitle("Data");

but I get this error

C:\root_v6.22.08_master-build\include\TRatioPlot.h:158:4: note: candidate constructor not viable: requires 0 arguments, but 2 were provided
   TRatioPlot();
   ^

it says that I don’tha e to pass arguments to TRatioPlot but if i dont’ pass argument, what does it plot?
Anyway, if I write

 auto rp1 = new TRatioPlot();
   rp1->Draw();
   rp1->GetLowerRefYaxis()->SetTitle("ratio");
   rp1->GetUpperRefYaxis()->SetTitle("entries");

the macro crashes

[couet]

@faca87

it says that I don’tha e to pass arguments to TRatioPlot but if i dont’ pass argument, what does it plot?

Look at the documentation, in particular the signature of the TRatioPlot constructors. None of them takes graphs. They you histograms .

[faca87]

Thank you @couet and isn’t there something like TRatioPlot available for Tgraph?

[couet]

No. I understand you want to have two pads. Just create the to pads at the right place and plot what you need in them.

[faca87]

Hello @couet, so I calculated the difference (column 4)
data.txt (328 Bytes)

and I added the code for the second
mulgr.cpp (2.8 KB) pad

but

1. I don’t get the second pad
2. I don’t get the the graph title in the first pad
   
   

[couet]

ratio->SetDrawOption("ALP");
should be :
ratio->Draw("ALP");

[faca87]

Thank you @couet,
I got the plot

but please…last 2 questions:

1. I would like to get the first pad higher than the second one as for example in this plot
   
   
   
   where the height of the plot on the top is higher than the one on the bottom

If I replace
TPad *pad2 = new TPad("pad2", "pad2", 0.0, 0.0, 1., 0.5);
by
TPad *pad2 = new TPad("pad2", "pad2", 0.0, 0.0, 1., 0.2);
you see…I’ve two problems:
a. it changes all the sizes (i.e. label title size too)
b. There is much space between the two pads…

So I would like to get the height of the first plot higher than the second one, but the space between them must not be so large

2. If I set the label title size, I don’t get the label titles

and if I set the label size the macro crashes!

here the update macro
mulgr.cpp (3.6 KB)

Thank you

[couet]

#include "TCanvas.h"
#include "TPad.h"
#include "TMultiGraph.h"
#include "TGraph.h"
#include "TGraphErrors.h"
#include "TAxis.h"
#include "TLegend.h"
#include "TLatex.h"
#include "TROOT.h"
#include "TRatioPlot.h"
#include <cstdlib>

void mulgr() {

   gStyle->SetOptFit();
   const char *datain = "data.txt";
   const char *dataout = "plot.pdf";
   TCanvas *c01 = new TCanvas("c01","multigraph",1280,1024);
   TPad *pad1 = new TPad("pad1", "pad1", 0.0, 0.3, 1.0, 1.0);
   pad1->SetGridx();         // Vertical grid
   pad1->Draw();             // Draw the upper pad: pad1
   pad1->cd();
   TMultiGraph *mg = new TMultiGraph();
   mg->SetTitle("Multi-graph Title");
   float offx=1.3;
   float offy=1.3;
   float margr=0.08;
   float w=3;
   float margl=0.12;
   float line=2;
   gPad->SetLeftMargin(margl);
   gPad->SetRightMargin(margr);
   TPaveText *t=new TPaveText(0.8,0.15,0.85,0.2,"brNDC");
   TGraphErrors *gr1 = new TGraphErrors(datain,"%lg %lg %*lg %*lg");
   gr1->SetMarkerColor(kBlue);
   gr1->SetLineColor(kBlue);
   gr1->SetMarkerStyle(3);
   gr1->SetMarkerSize(1.3);
   gr1->SetLineWidth(line);
   gr1->SetDrawOption("AP");
   mg->Add(gr1);
   TGraphErrors *gr2 = new TGraphErrors(datain,"%lg %*lg %lg %*lg");
   gr2->SetMarkerColor(kRed);
   gr2->SetLineColor(kRed);
   gr2->SetMarkerStyle(5);
   gr2->SetMarkerSize(1.3);
   gr2->SetLineWidth(line);
   gr2->SetDrawOption("P");
   mg->Add(gr2);
   mg->Draw("ALP");
   c01->Modified();
   c01->Update();
   mg->GetXaxis()->SetTitle("x");
   mg->GetXaxis()->SetLimits(0.5,12.5);
   mg->GetYaxis()->SetTitle("y");
   mg->GetYaxis()->SetTitleOffset(offy);
   mg->GetXaxis()->SetTitleOffset(offx);
   mg->GetXaxis()->SetLabelFont(43);
   mg->GetXaxis()->SetLabelSize(20);
   mg->GetYaxis()->SetLabelFont(43);
   mg->GetYaxis()->SetLabelSize(20);
   mg->GetXaxis()->SetTitleFont(43);
   mg->GetXaxis()->SetTitleSize(20);
   mg->GetYaxis()->SetTitleFont(43);
   mg->GetYaxis()->SetTitleSize(20);
   c01->Modified();
   c01->Update();

   TLegend* leg = new TLegend(0.15, 0.75, .2, .85);
   leg->SetHeader("Legend");
   leg->SetNColumns(1);
   leg->AddEntry(gr1, "gr1", "AP");
   leg->AddEntry(gr2, "gr2", "P");
   leg->Draw();

   gPad->Update();
   t->AddText("Text");
   t->Draw();
   c01->cd();
   c01->Update();
   TPad *pad2 = new TPad("pad2", "pad2", 0.0, 0.0, 1.0, 0.3);
   pad2->SetTopMargin(0.0);
   pad2->SetGridx(); // vertical grid
   pad2->Draw();
   pad2->cd();       // pad2 becomes the current pad
   gPad->SetLeftMargin(margl);
   gPad->SetRightMargin(margr);
   TGraphErrors *ratio = new TGraphErrors(datain,"%lg %*lg %*lg %lg");
   ratio->SetTitle(" ");
   ratio->SetMarkerColor(kGreen+3);
   ratio->SetLineColor(kGreen+3);
   ratio->SetLineWidth(3);
   ratio->SetMarkerSize(2);
   ratio->SetMarkerStyle(29);
   ratio->Draw("ALP");
   ratio->GetXaxis()->SetLimits(0.5,12.5);
   ratio->GetXaxis()->SetLabelFont(43);
   ratio->GetXaxis()->SetLabelSize(20);
   ratio->GetYaxis()->SetLabelFont(43);
   ratio->GetYaxis()->SetLabelSize(20);
   ratio->GetXaxis()->SetTitleFont(43);
   ratio->GetXaxis()->SetTitleSize(20);
   ratio->GetYaxis()->SetTitleFont(43);
   ratio->GetYaxis()->SetTitleSize(20);
   ratio->GetXaxis()->SetTitle("x");
   ratio->GetYaxis()->SetTitle("ratio");
   ratio->GetYaxis()->SetTitleOffset(offy);
   ratio->GetXaxis()->SetTitleOffset(offx);
   c01->Modified();
   c01->Update();
   c01->Print(dataout);
}

[faca87]

Sorry @couet I noticed 2 problems

1. gStyle->SetTitleSize(0.05);
   doesn’t change the title size

2. !
   the title of x-axis of the pad2 cover the number 12 then I think the pads should be a bit lower and a bottom space is needed, but the command

``pad2->SetBottomMargin(3);`

doesn’t work
Moreover, I added a code

void DrawVerticalLine(Double_t x)
{
   TLine l;
   Double_t lm = gPad->GetLeftMargin();
   Double_t rm = 1.-gPad->GetRightMargin();
   Double_t tm = 1.-gPad->GetTopMargin();
   Double_t bm = gPad->GetBottomMargin();
   Double_t xndc = (rm-lm)*((x-gPad->GetUxmin())/(gPad->GetUxmax()-gPad->GetUxmin()))+lm;
   l.DrawLineNDC(xndc,bm,xndc,tm);
}

float threshold = 0;
			auto lnThreshold = new TLine(0, threshold, gPad->GetUxmax(),threshold);
			lnThreshold->SetLineColor(kRed);
			lnThreshold->SetLineStyle(10);
			lnThreshold->SetLineWidth(2.);  // maybe
			lnThreshold->Draw();
			//DrawVerticalLine(2.);
            gPad->Modified();

that I use to draw a line on 0 in the second pad (I used this code in other plots) but in this case the line starts out of the the plot

Thanks

[couet]

#include "TCanvas.h"
#include "TPad.h"
#include "TMultiGraph.h"
#include "TGraph.h"
#include "TGraphErrors.h"
#include "TAxis.h"
#include "TLegend.h"
#include "TLatex.h"
#include "TROOT.h"
#include "TRatioPlot.h"
#include <cstdlib>

void mulgr() {

   gStyle->SetOptFit();
   const char *datain = "data.txt";
   const char *dataout = "plot.pdf";
   TCanvas *c01 = new TCanvas("c01","multigraph",1280,1024);
   TPad *pad1 = new TPad("pad1", "pad1", 0.0, 0.3, 1.0, 1.0);
   pad1->SetGridx();         // Vertical grid
   pad1->Draw();             // Draw the upper pad: pad1
   pad1->cd();
   gStyle->SetTitleFontSize(0.05);
   TMultiGraph *mg = new TMultiGraph();
   mg->SetTitle("Multi-graph Title");
   float offx=1.3;
   float offy=1.3;
   float margr=0.08;
   float w=3;
   float margl=0.12;
   float line=2;
   float xl1 = 0.5, xl2 = 12.5;
   gPad->SetLeftMargin(margl);
   gPad->SetRightMargin(margr);
   TPaveText *t=new TPaveText(0.8,0.15,0.85,0.2,"brNDC");
   TGraphErrors *gr1 = new TGraphErrors(datain,"%lg %lg %*lg %*lg");
   gr1->SetMarkerColor(kBlue);
   gr1->SetLineColor(kBlue);
   gr1->SetMarkerStyle(3);
   gr1->SetMarkerSize(1.3);
   gr1->SetLineWidth(line);
   gr1->SetDrawOption("AP");
   mg->Add(gr1);
   TGraphErrors *gr2 = new TGraphErrors(datain,"%lg %*lg %lg %*lg");
   gr2->SetMarkerColor(kRed);
   gr2->SetLineColor(kRed);
   gr2->SetMarkerStyle(5);
   gr2->SetMarkerSize(1.3);
   gr2->SetLineWidth(line);
   gr2->SetDrawOption("P");
   mg->Add(gr2);
   mg->Draw("ALP");
   c01->Modified();
   c01->Update();
   mg->GetXaxis()->SetTitle("x");
   mg->GetXaxis()->SetLimits(xl1,xl2);
   mg->GetYaxis()->SetTitle("y");
   mg->GetYaxis()->SetTitleOffset(offy);
   mg->GetXaxis()->SetTitleOffset(offx);
   mg->GetXaxis()->SetLabelFont(43);
   mg->GetXaxis()->SetLabelSize(20);
   mg->GetYaxis()->SetLabelFont(43);
   mg->GetYaxis()->SetLabelSize(20);
   mg->GetXaxis()->SetTitleFont(43);
   mg->GetXaxis()->SetTitleSize(20);
   mg->GetYaxis()->SetTitleFont(43);
   mg->GetYaxis()->SetTitleSize(20);
   c01->Modified();
   c01->Update();

   TLegend* leg = new TLegend(0.15, 0.75, .2, .85);
   leg->SetHeader("Legend");
   leg->SetNColumns(1);
   leg->AddEntry(gr1, "gr1", "AP");
   leg->AddEntry(gr2, "gr2", "P");
   leg->Draw();

   gPad->Update();
   t->AddText("Text");
   t->Draw();
   c01->cd();
   c01->Update();
   TPad *pad2 = new TPad("pad2", "pad2", 0.0, 0.0, 1.0, 0.3);
   pad2->SetTopMargin(0.0);
   pad2->SetGridx(); // vertical grid
   pad2->Draw();
   pad2->cd();       // pad2 becomes the current pad
   gPad->SetLeftMargin(margl);
   gPad->SetRightMargin(margr);
   gPad->SetBottomMargin(0.15);

   TGraphErrors *ratio = new TGraphErrors(datain,"%lg %*lg %*lg %lg");
   ratio->SetTitle(" ");
   ratio->SetMarkerColor(kGreen+3);
   ratio->SetLineColor(kGreen+3);
   ratio->SetLineWidth(3);
   ratio->SetMarkerSize(2);
   ratio->SetMarkerStyle(29);
   ratio->Draw("ALP");
   ratio->GetXaxis()->SetLimits(xl1,xl2);
   ratio->GetXaxis()->SetLabelFont(43);
   ratio->GetXaxis()->SetLabelSize(20);
   ratio->GetYaxis()->SetLabelFont(43);
   ratio->GetYaxis()->SetLabelSize(20);
   ratio->GetXaxis()->SetTitleFont(43);
   ratio->GetXaxis()->SetTitleSize(20);
   ratio->GetYaxis()->SetTitleFont(43);
   ratio->GetYaxis()->SetTitleSize(20);
   ratio->GetXaxis()->SetTitle("X Axis Title");
   ratio->GetXaxis()->SetTitleOffset(3.5);
   ratio->GetYaxis()->SetTitle("Ratio");
   ratio->GetYaxis()->SetTitleOffset(offy);

   float threshold = 0;
   auto lnThreshold = new TLine(xl1, threshold, xl2 ,threshold);
   lnThreshold->SetLineColor(kRed);
   lnThreshold->SetLineStyle(10);
   lnThreshold->SetLineWidth(2.);  // maybe
   lnThreshold->Draw();

   c01->Modified();
   c01->Update();
   c01->Print(dataout);
}

[faca87]

Thank you for all the help @couet!