Can't call TGraph function

ROOT
1

Hello,

I’m writing a code to specify an optical system.

I’m stuck with this in calling TGraph, and I really don’t understand, since I already done this in other codes.

The error I get is this:

Error: Can’t call TGraph::TGraph(n_points_GSD,GSD,Optical_Diameter_1) in current scope Optical_System_2.C:95:
Possible candidates are…
(in TGraph)
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(void);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(Int_t n);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(Int_t n,const Int_t* x,const Int_t* y);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(Int_t n,const Float_t* x,const Float_t* y);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(Int_t n,const Double_t* x,const Double_t* y);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const TGraph& gr);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const TVectorF& vx,const TVectorF& vy);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const TVectorD& vx,const TVectorD& vy);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const TH1* h);
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const TF1* f,Option_t* option="");
/usr/lib/x86_64-linux-gnu/root5.34/libHist.so -1:-1 0 public: TGraph TGraph::TGraph(const char* filename,const char* format="%lg %lg",Option_t* option="");
Error: Illegal Assignment to an undeclared symbol Gra1 Optical_System_2.C:95:
*** Interpreter error recovered ***

And my code is:

void Optical_System_2(){

// Earth Radius, Mass and Graviational Constant
double Rt,Mt,Gt;
Rt = 6.371e6; // m
Mt = 5.972e24; // kg
Gt = 6.67384e-11; // m3.kg-1.s-2

// Planck Constant & Light Speed
double h,c;
h = 6.6262e-34; // J.s
c = 3.0e8; // m.s-1

// Integration Time Constant
double K_int = 0.5;

// Input Parameters
double Electronic_Noise = 80.;
double Quantum_Eff = 0.5;

double Radiance1,Radiance2;
Radiance1 = 1.4; // W.m-2.sr-1.um-1
Radiance2 = 36.; // W.m-2.sr-1.um-1

// Altitude, Optical Transmittance
double GSD,H,L_km,T_opt,lambda,BW,Visibility;
//GSD = 10.; // m
H = 600.e3; // m
L_km = 4.; // km
T_opt = 0.7;

// Central Wavelength, Bandwidth & Visibility
lambda = 0.59; BW = 0.15; // um
Visibility = 15; // km

// Signal To Noise Ratio -> INPUT VALUES
const int SNR1 = 40; // dB
const int SNR2 = 100; // dB
const int n_points_SNR = SNR2-SNR1+1;
double SNR[n_points_SNR];

// Ground Sample Distance -> INPUT VALUES
int GSD1 = 5; // m
int GSD2 = 20; // m
const int n_points_GSD = GSD2-GSD1+1;
double GSD[n_points_GSD];

// Atmospheric Transmittance
double T_atm = exp(-2.77L_km/(Visibilitypow(lambda,0.7)));

// Vectors Definition
double Omega[n_points_GSD][n_points_SNR];
double T_int[n_points_GSD][n_points_SNR];

double Alpha[n_points_GSD][n_points_SNR];
double Beta[n_points_GSD][n_points_SNR];
double Optical_Diameter[n_points_GSD][n_points_SNR];

double Optical_Diameter_1[n_points_GSD];
double Optical_Diameter_2[n_points_GSD];
double Optical_Diameter_3[n_points_GSD];

for(int i=0;i<n_points_GSD;i++){
for(int j=0;j<n_points_SNR;j++){

  GSD[i] = i+GSD1;
  SNR[j] = j+SNR1;

  Omega[i][j] = pow((GSD[i])/H,2);
  T_int[i][j] = K_int*(GSD[i])/sqrt((Gt*Mt)/(H+Rt));
  
  Alpha[i][j] = 4*h*c*Electronic_Noise*pow(10,(SNR[j])/20);
  Beta[i][j] = Quantum_Eff*Radiance2*T_atm*Omega[i][j]*BW*T_opt*T_int[i][j]*lambda*TMath::Pi();
  
  Optical_Diameter[i][j] = 1e5*sqrt(Alpha[i][j]/Beta[i][j]);
                    
}
cout<<"GSD = "<<GSD[i]<<endl;

}

for(int k=0;k<n_points_GSD;k++)
{
Optical_Diameter_1[k] = Optical_Diameter[k][10];
Optical_Diameter_2[k] = Optical_Diameter[k][20];
Optical_Diameter_3[k] = Optical_Diameter[k][30];

cout<<"Optical_Diameter_1 = "<<Optical_Diameter_1[k]<<endl;

}
//cout<<" = "<<GSD[5]<<endl;

cout<<"n_points_GSD = "<<n_points_GSD<<endl;
cout<<"n_points_SNR = "<<n_points_SNR<<endl;

// Plotting Section :: Creating Canvas
TCanvas *c1 = new TCanvas(“c1”);
c1->SetFillColor(10);
c1->SetGrid();

Gra1 = new TGraph(n_points_GSD,GSD,Optical_Diameter_1);
Gra1->SetLineColor(4);
Gra1->SetLineWidth(4);
Gra1->SetTitle(“Optical System Specification”);
Gra1->GetXaxis()->SetTitle(“GSD [m]”);
Gra1->GetYaxis()->SetTitle(“Optics Diameter [cm]”);
Gra1->DrawClone();
}

A I see in the error message, TGraph accepts as input (int, double, double), which is what I’m doing.

Thank you for the help.

Best Regards.

2

Always try to precompile your macro using ACLiC, in order to find source code problems, e.g. try something like:
root [0] .L Optical_System_2.cxx++

#include “TCanvas.h”
#include “TGraph.h”
#include “TAxis.h”
#include “TMath.h”
#include
// …
double GSD0,H,L_km,T_opt,lambda,BW,Visibility;
//GSD0 = 10.; // m
// …
TGraph *Gra1 = new TGraph(n_points_GSD,GSD,Optical_Diameter_1);
// …

3

Hello,

Thank you for your help!!

With the pre-compilation I found the problem, which was that I had already declared the variable GSD as another kind before:

/home/lghizoni/Documents/EQSA/WFI/Optics System Specification/./Optical_System_2.cpp:52:26: error: conflicting declaration ‘double GSD [(long int)n_points_GSD]’
double GSD[n_points_GSD];

Thanks a lot. Now I’ll always precompile before :smiley:

Best Regards.
Leonardo.