Hi
I'm trying to display a TH2F as a lego plot using spherical coordinates.
The two dimensions of my histogram are theta and phi and with field
strength E given as the value. When I plot this in spherical coordinates
the value of r is fixed and independent of E, this gives the appearance of
a value for E where in fact the value of E is zero. Is there any option to
set the value of r to zero or a negligible value?
cheers
steve.
{
/***********************************************************************
Macro Name: E_field_ntuple.cxx
macro to create a ntuple with values taken from file: Efield.dat
author: Steve Aplin Date:
**********************************************************************/
gROOT->Reset("a");
Float_t c_0 = 2.99e8; // speed of light in free space
Int_t Nv = 4; // Number of points of v
Int_t Nr = 10; // Number of points of r
Int_t Ntheta = 9; // Number of points of theta
Int_t Nphi = 16; // Number of points of phi
Float_t v; // Velocity of point charge
Float_t r; // radius from charge in meters
Float_t phi; // phi in degrees
Float_t theta; // theta in degrees
Float_t theta_rad;
Float_t x; // cartesian co-ordinate
Float_t y; // cartesian co-ordinate
Float_t z; // cartesian co-ordinate
Float_t Er; // Value of Electric field strength
// create File "rootfile.root" to write output to
TFile *rootfile = new TFile("rootfile.root","RECREATE");
// create Canvas "Electric Field Plots" // ,(top right),(size hz,vrt)
c1 = new TCanvas("c1","Electric Field Plots", 200,10,900,700);
//,(bot_left),(top_right),(colour)
pad1 = new TPad("pad1","This is pad1",0.02,0.52,0.48,0.98,21);
pad2 = new TPad("pad2","This is pad2",0.52,0.52,0.98,0.98,21);
pad3 = new TPad("pad3","This is pad3",0.02,0.02,0.48,0.48,21);
pad4 = new TPad("pad4","This is pad4",0.52,0.02,0.98,0.48,21);
pad1->Draw();
pad2->Draw();
pad3->Draw();
pad4->Draw();
// create ntuple "ntuple"
TNtuple *ntuple = new TNtuple("ntuple","E field","Er:v:r:theta:phi:x:y:z");
// create Histogram "Field_Map_v_0c"
TH2F *Field_Map_v_0c = new TH2F("Field_Map_v_0c",
"v = 0",16,0,360,10,0,1 );
// create Histogram "Field_Map_v_05c"
TH2F *Field_Map_v_05c = new TH2F("Field_Map_v_05c",
"v = 0.5c",16,0,360,10,0,1 );
// create Histogram "Field_Map_v_09c"
TH2F *Field_Map_v_09c = new TH2F("Field_Map_v_09c",
"v = 0.9c",16,0,360,10,0,1 );
// create Histogram "Field_Map_v_099c"
TH2F *Field_Map_v_099c = new TH2F("Field_Map_v_099c",
"v = 0.99c",16,0,360,10,0,1 );
ifstream data_file("E_field.dat"); // The input file
if (data_file.bad()) // check for bad file open
{
cerr << "Error: could not open E_field.dat\n";
exit (8);
}
for (Int_t i = 0; i < Nv; i++)
{
for (Int_t j = 0; j < Nr; j++)
{
for (Int_t k = 0; k < Ntheta; k++)
{
for (Int_t l = 0; l < Nphi; l++)
{
data_file >> Er >> v >> r >> theta >> phi >> x >> y >> z;
//Take value from
// file and assign
theta_rad = theta / 57.3;
ntuple->Fill(Er,v,r,theta,phi,x,y,z);
// fill ntuple with
// values
if ((theta == 0) || (theta == 180)) l = Nphi;
// to prevent looping over phi at singular points of theta
}
// fill histogram bin
if ( i == 0 ){
Field_Map_v_0c->SetBinContent
(Field_Map_v_0c->GetBin((theta/180*8)+0.5, r*10-.5), Er);
Field_Map_v_0c->SetBinContent
(Field_Map_v_0c->GetBin((theta/180*8)+8.5, r*10-.5), Er);
}
// fill histogram bin
if ( i == 1 ){
Field_Map_v_05c->SetBinContent
(Field_Map_v_05c->GetBin((theta/180*8)+.5,(r*10)-.5), Er);
Field_Map_v_05c->SetBinContent
(Field_Map_v_05c->GetBin((theta/180*8)+8.5,(r*10)-.5), Er);
}
// fill histogram bin
if ( i == 2 ){
Field_Map_v_09c->SetBinContent
(Field_Map_v_09c->GetBin((theta/180*8)+.5,(r*10)-.5), Er);
Field_Map_v_09c->SetBinContent
(Field_Map_v_09c->GetBin((theta/180*8)+8.5,(r*10)-.5), Er);
}
// fill histogram bin
if ( i == 3 ){
Field_Map_v_099c->SetBinContent
(Field_Map_v_099c->GetBin((theta/180*8)+.5,(r*10)-.5), Er);
Field_Map_v_099c->SetBinContent
(Field_Map_v_099c->GetBin((theta/180*8)+8.5,(r*10)-.5), Er);
}
}
}
}
pad1->cd();
Field_Map_v_0c->Draw("lego1 pol");
pad2->cd();
Field_Map_v_05c->Draw("lego1 pol");
pad3->cd();
Field_Map_v_09c->Draw("lego1 pol");
pad4->cd();
Field_Map_v_099c->Draw("lego1 pol");
ntuple->Scan("Er:v", "(r == 1.0)&&(theta == 90)&&(phi==0)");
rootfile->Write(); // write ntuple to
// file
//rootfile->Close();
}
This archive was generated by hypermail 2b29 : Tue Jan 02 2001 - 11:50:19 MET