使用“用户坐标”而不是 bin 编号来设置范围更方便。且允许用户直接在直方图对象上TH::SetAxisRange(min, max, "axis")设置轴范围，而无需使用Get[XYZ]axis()。E.g.
hpxpy->GetYaxis()->SetRangeUser(0., 3.);
等价于：
hpxpy->SetAxisRange(0., 3.,"Y");
支持绘制图形后更改轴范围：
{
auto c = new TCanvas("c","A Zoomed Graph",200,10,700,500);
int n = 10;
double x[10] = {-.22,.05,.25,.35,.5,.61,.7,.85,.89,.95};
double y[10] = {1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
auto gr = new TGraph(n,x,y);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(20);
gr->Draw("ALP");
gr->GetXaxis()->SetRangeUser(0, 0.5);
gr->GetYaxis()->SetRangeUser(1, 8);
}
{
auto c = new TCanvas("c","A Zoomed Graph",200,10,700,500);
c->DrawFrame(0,1,0.5,8);
int n = 10;
double x[10] = {-.22,.05,.25,.35,.5,.61,.7,.85,.89,.95};
double y[10] = {1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
auto gr = new TGraph(n,x,y);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(20);
gr->Draw("LP");
}
void transpad()
{
TCanvas *c1 = new TCanvas("c1","transparent pad",200,10,700,500);
TPad *pad1 = new TPad("pad1","",0,0,1,1);
TPad *pad2 = new TPad("pad2","",0,0,1,1);
pad1->Draw();
pad2->SetFillStyle(4000); //will be transparent
pad1->cd();
TH1F *h1 = new TH1F("h1","h1",100,-3,3);
TH1F *h2 = new TH1F("h2","h2",100,-3,3);
TRandom r;
for (Int_t i=0;i<100000;i++) {
Double_t x1 = r.Gaus(-1,0.5);
Double_t x2 = r.Gaus(1,1.5);
if (i <1000) h1->Fill(x1);
h2->Fill(x2);
}
h1->Draw();
pad1->Update(); //this will force the generation of the "stats" box
TPaveStats *ps1 = (TPaveStats*)h1->GetListOfFunctions()->FindObject("stats");
ps1->SetX1NDC(0.4); ps1->SetX2NDC(0.6);
pad1->Modified();
c1->cd();
//compute the pad range with suitable margins
Double_t ymin = 0;
Double_t ymax = 2000;
Double_t dy = (ymax-ymin)/0.8; //10 per cent margins top and bottom
Double_t xmin = -3;
Double_t xmax = 3;
Double_t dx = (xmax-xmin)/0.8; //10 per cent margins left and right
pad2->Range(xmin-0.1*dx,ymin-0.1*dy,xmax+0.1*dx,ymax+0.1*dy);
pad2->Draw();
pad2->cd();
h2->SetLineColor(kRed);
// h2->Draw("][sames");
h2->Draw("sames");
pad2->Update();
TPaveStats *ps2 = (TPaveStats*)h2->GetListOfFunctions()->FindObject("stats");
ps2->SetX1NDC(0.65); ps2->SetX2NDC(0.85);
ps2->SetTextColor(kRed);
// draw axis on the right side of the pad
TGaxis *axis = new TGaxis(xmax,ymin,xmax,ymax,ymin,ymax,50510,"+L");
axis->SetLabelColor(kRed);
axis->Draw();
}
显示两个不同比例的直方图的画布示例-利用缩放
#include "TCanvas.h"
#include "TStyle.h"
#include "TH1.h"
#include "TGaxis.h"
#include "TRandom.h"
void twoscales()
{
TCanvas *c1 = new TCanvas("c1","hists with different scales",600,400);
//create/fill draw h1
gStyle->SetOptStat(kFALSE);
TH1F *h1 = new TH1F("h1","my histogram",100,-3,3);
Int_t i;
for (i=0;i<10000;i++) h1->Fill(gRandom->Gaus(0,1));
h1->Draw();
c1->Update();
//create hint1 filled with the bins integral of h1
TH1F *hint1 = new TH1F("hint1","h1 bins integral",100,-3,3);
Float_t sum = 0;
for (i=1;i<=100;i++) {
sum += h1->GetBinContent(i);
hint1->SetBinContent(i,sum);
}
//scale hint1 to the pad coordinates
Float_t rightmax = 1.1*hint1->GetMaximum();
Float_t scale = gPad->GetUymax()/rightmax;
hint1->SetLineColor(kRed);
hint1->Scale(scale);
hint1->Draw("same");
//draw an axis on the right side
TGaxis *axis = new TGaxis(gPad->GetUxmax(),gPad->GetUymin(),
gPad->GetUxmax(), gPad->GetUymax(),0,rightmax,510,"+L");
axis->SetLineColor(kRed);
axis->SetLabelColor(kRed);
axis->Draw();
}
void gaxis(){
auto c1 = new TCanvas("c1","Examples of TGaxis",10,10,700,500);
c1->Range(-10,-1,10,1);
auto axis1 = new TGaxis(-4.5,-0.2,5.5,-0.2,-6,8,510,"");
axis1->Draw();
auto axis2 = new TGaxis(-4.5,0.2,5.5,0.2,0.001,10000,510,"G");
axis2->Draw();
auto axis3 = new TGaxis(-9,-0.8,-9,0.8,-8,8,50510,"");
axis3->SetTitle("axis3");
axis3->SetTitleOffset(0.5);
axis3->Draw();
auto axis4 = new TGaxis(-7,-0.8,-7,0.8,1,10000,50510,"G");
axis4->SetTitle("axis4");
axis4->Draw();
auto axis5 = new TGaxis(-4.5,-0.6,5.5,-0.6,1.2,1.32,80506,"-+");
axis5->SetLabelSize(0.03);
axis5->SetTextFont(72);
axis5->Draw();
auto axis6 = new TGaxis(-4.5,0.5,5.5,0.5,100,900,50510,"-");
axis6->Draw();
auto axis7 = new TGaxis(-5.5,0.85,5.5,0.85,0,4.3e-6,510,"");
axis7->Draw();
auto axis8 = new TGaxis(8,-0.8,8,0.8,0,9000,50510,"+L");
axis8->Draw();
// One can make a vertical axis going top->bottom. However the two x values should be
// slightly different to avoid labels overlapping.
auto axis9 = new TGaxis(6.5,0.8,6.499,-0.8,0,90,50510,"-");
axis9->Draw();
}
断轴画法
共用轴/拼接轴画法
共轴画法是一种常见的绘图技巧，在同一张 canvas 中绘制多图并共享 X 轴或 Y 轴。这种方式常用于比较不同数据集之间的趋势或关系。最简单的共轴画法是TCanvas::Divide(numberx, numbery, 0)。
void seism(){
//TStopwatch sw;sw.Start();
//TDatime dtime;
//gStyle->SetTimeOffset( dtime.Convert() ); // replace axis with timeaxis
//cout << dtime.Convert() << endl;
TCanvas *c1 = new TCanvas("seism","Time on axis",0,0,1000,500);
// TCanvas("canvas name","canvas title",the pixel coordinates of the top left corner of canvas,same as above,size of pixel along X,size of pixel along Y)
c1->SetFillColor( 42 ); // fill background color
c1->SetFrameFillColor( 33 ); // color in frame
c1->SetGrid(); // add grid in the frame
Float_t bintime =1; // set one bin = 1 second. change it to set time scale,don't chenge real time
TH1F *ht = new TH1F("ht","The ROOT seism",10,0,10*bintime);
// TH1 = 1D histogram;F = float;("name","title",bin,Xmin,Xmax)
Float_t signal = 700;
// c/c++ : int , float , double
// POOT :int_t , float_t , double_t
ht->SetMaximum( signal );
ht->SetMinimum( -signal );
ht->SetStats( 1 ); // set statistic pad,1=display,0=hide
ht->SetLineColor( 2 );
ht->GetXaxis()->SetTimeDisplay( 1 ); // settimedisplay,1=display,0=hide
ht->GetYaxis()->SetNdivisions( 220 ); // n1n2n3,n1 = a bin in the bin;n2n3 = ???
ht->Draw();
for(int i=0;i<200;i++){
// build a signal ; noisy damped sine
Float_t noise = gRandom->Gaus(0,120);
if(i>100){ noise = noise + sin((i-700)*6.28/30)*exp((700-i)/300); }
ht->SetBinContent(i,noise); // the ith content is noise
c1->Modified();
c1->Update();
gSystem->ProcessEvents();
}
//printf("real time =%8.3fs,cpu time =%8.3fsn", sw.RealTime(), sw.CpuTime());
return 0;
}
{
auto c = new TCanvas("c","c",0,0,500,500);
c->Range(-11,-11,11,11);
auto f2 = new TF1("x2","x*x",-10,10);
f2->SetLineColor(kRed);
f2->Draw("same");
auto f3 = new TF1("x3","x*x*x",-10,10);
f3->SetLineColor(kBlue);
f3->Draw("same");
// Draw the axis with arrows
auto ox = new TGaxis(-10,0,10,0,-10.,10.,510,"+-S>");
ox->SetTickSize(0.009);
ox->SetLabelFont(42);
ox->SetLabelSize(0.025);
ox->Draw();
auto oy = new TGaxis(0,-10,0,10,-10,10,510,"+-S>");
oy->SetTickSize(0.009);
oy->SetLabelFont(42);
oy->SetLabelSize(0.025);
oy->Draw();
}
画面留白
c1 = new TCanvas("c1","A Simple Graph ",300,0,750,560); c1->SetLeftMargin(0.12);, c1->SetBottomMargin(0.10);
