Analysis of long Double data with TTree?

ROOT
1

Hello,

I have a problem while analysis of long Double data type with TTree. I want to analyse following data as:

Time_(s) s0
0.00000E+000 0.00000E+000
5.09966E-002 0.00000E+000
6.62959E-001 0.00000E+000
2.09959E+000 0.00000E+000
4.38372E+000 0.00000E+000
7.62890E+000 0.00000E+000
1.17973E+001 0.00000E+000
1.69840E+001 0.00000E+000
2.31787E+001 0.00000E+000
3.04986E+001 0.00000E+000
3.90199E+001 1.04312E+003
4.88280E+001 6.56040E+003
5.99976E+001 1.70816E+004
7.26286E+001 2.81410E+004

For this my code is as follows:

void Analyse() {
  
//DecIaration of Ieaves types
long double time, s0;
   
   FILE *fp = fopen("C:/Analyse.data", "r");
   char line[128];
   //create the file, the Tree and a few branches
   TFile *rootf = new TFile("Analyse.root", "RECREATE");
   
   TTree *tree = new TTree("tree","Tree");	
   
   tree->Branch("time",&time,"time/D");
   tree->Branch("s0",&s0,"s0/D");       
            
    while (fgets(&line[0],127,fp)) {
      sscanf(&line[0],"%lf%lf",&zeit,&s0);    
        tree->Fill();
   }
  tree->Print(); 
  tree->Write();
  fclose(fp);
  rootf->Write();
  //Analysis
   TFile *f1 = TFile::Open("Analyse.root");
   //read a tree from a root file
   TTree *T1 = (TTree*)f1->Get("tree");
    TCanvas *c = new TCanvas("c", "c", 0, 0, 1000, 1000);
    T1->Draw("s0:time");
     gPad->Modified(); 
     gPad->Update();
     TGraph *gr = (TGraph *)gPad->GetPrimitive("Graph")->Clone();
     TGraph *gr = new TGraph(T1->GetSelectedRows(),T1->GetV2(), T1->GetV1());
     gr->Draw("AC");      [color=#FF0000]//Here I am not getting a proper curve as I expected for analysis. I want a proper Curve for analysis and for fitting a function[/color]
     gr->SetMarkerStyle(2);
     gr->SetLineColor(16);
}

what is going wrong? Is there other way to analyse long double data type? Please guide me.

2

You do not “Fit” anything so there is no “fitting function” which can be drawn.
See also TGraphPainter and TGraph::Fit.

3

Hello,

Thanks. I want to fit a function afterwards. But currently I am not getting a proper graph as I expected.
I wants to fit the following function:

TF1 *f = new TF1(“f”, “exp([0]+[1]*x)”, -1,8);
gr->Fit(f, “R”);

Here I am attaching .pdf file of a graph plot which I am gtting with the above code. A graph plot itself is not as I want.
Analyse.pdf (25.5 KB)

4

[code]#include “TFile.h”
#include “TTree.h”
#include “TCanvas.h”
#include “TPad.h”
#include “TGraph.h”

#include

void Analyse() {
//DecIaration of Ieaves types
Double_t time, s0;

//create the file, the Tree and a few branches
TFile *rootf = new TFile(“Analyse.root”, “RECREATE”);

TTree *tree = new TTree(“tree”,“Tree”);

tree->Branch(“time”,&time,“time/D”);
tree->Branch(“s0”,&s0,“s0/D”);

FILE *fp = fopen(“C:/Analyse.data”, “r”);
char line[128];
while (fgets(&line[0],127,fp)) {
sscanf(&line[0],"%lf%lf",&time,&s0);
tree->Fill();
}
fclose(fp);

tree->Print();
tree->Write();
delete rootf;

//Analysis
TCanvas *c = new TCanvas(“c”, “c”, 0, 0, 1000, 1000);
c->Divide(1, 2);

TFile *f1 = TFile::Open(“Analyse.root”);
//read a tree from a root file
TTree *T1; f1->GetObject(“tree”, T1);

c->cd(1);
T1->SetMarkerStyle(20);
T1->Draw(“s0:time”);
gPad->Modified(); gPad->Update();

c->cd(2);
// TGraph *gr = (TGraph *)gPad->GetPrimitive(“Graph”)->Clone();
TGraph *gr = new TGraph(T1->GetSelectedRows(),T1->GetV2(), T1->GetV1());
gr->SetMarkerStyle(20);
gr->SetLineColor(16);
// “expo” = “exp([0]+[1]*x)” http://root.cern.ch/root/html/TFormula.html
gr->Fit(“expo”);
gr->Draw(“AP”);
gPad->Modified(); gPad->Update();
}[/code]

5

Hello,

Thanks for the guidance. It works. But I don’t want to use, gr->SetMarkerStyle(20); and gr->Draw(“AP”); Instead I want gr->Draw(“AC”); Means a axis with a smoot curve. When I use “AC” option then I got the output as file attached here with.
Any soluction to get a smooth curve ?

6

Why don’t you simply change … gr->Draw(“AP”); … into … gr->Draw(“AC”); … and see what happens?

7

For representing a result in the form of a Curve as per requirment. So I want to use “AC” option instead “AP”.

8

Note that with AC and AL points are connected together in the order they appear in the X vector. So if the X vector is not sorted you will get something similar to the plot you posted. Also be careful wih th C option it might add some artefacts when the points are random, far to each other, or with a big gradient between them. Have a first try with L instead of C.

9

Do not hesitate, use it.

10

Hello,

Yes, you are right. Its an experimental data to be analysed. Some of the data changes with a big gradient between them. I tried with temporary deleting those records then with AC it works. But as I want to analyse a data I have to use “AC” option. I tried with “AL” option but I gets the output as a file attached here with, which is not relevant.

You said if the X Vector is not sorted. Could you explain in detail? I understand, I need to sort my values which are representing on X axis. But I can not do so because, its an experimental data and need to be get ploted as it is e.g: time Vs dataValues. Could you further guide me to overcome with these problem?

Thank you in advance.

11

I do not see the file… And please USE AL … you will get problem with AC

So do not use neither AC or AL … you will get grap plots impossible to read.
use AP as stated before.

12

[quote=“Pree”]You said if the X Vector is not sorted. Could you explain in detail? I understand, I need to sort my values which are representing on X axis. But I can not do so because, its an experimental data and need to be get ploted as it is e.g: time Vs dataValues. Could you further guide me to overcome with these problem?
[/quote]

If you need data sorted you have to sort it.
There is a nice std::sort function, which will do a work for you. You only have to think how to organize a data in a such way, that you sort not individual x-values, but (x,y) pairs, using x as a criteria.
This will require at least 3 additional buffers (one for pair, two for 2 separate xs/ys arrays ), and it’s quite ugly, but at least it’ll work. If you still need a help, I can give a code sketch.

BTW I think we can add some special hint parameter for TGraph (or additional constructor) to let it know, that it should sort data (though it can be non-trivial sometimes).

13

Or even the ROOT one: TMath:Sort()

14

There exists TGraph::Sort.
Simply try to add “gr->Sort();”, before you “Fit” and/or “Draw” it.

15

Yes true :slight_smile: I forgot this one :slight_smile:

16

Hello All,

Thanks a lot for a guidance. Yes, it works after using gr->Sort();