Scott Sampson wrote:
>
> Hi,
>
> I want to fill a histogram with a color after it is plotted, but only on a
> specified x-range. Is there a way to do this? Also, Is it possible to
> shade a entire section of a plot? i.e. the have fill color above and
> below the histogram line in a specified x-range? Thanks,
>
> Scott
The example below illustrates one of the many ways to do it.
The example must be run with Root 2.00/07.
To execute, simply do;
Root > .x scott.C
Rene Brun
//----file scott.C
Double_t g2(Double_t *x, Double_t *par)
{
Double_t e0 = (x[0]-par[1])/par[2];
Double_t g0 = par[0]*TMath::Exp(-0.5*e0*e0);
Double_t e1 = (x[0]-par[4])/par[5];
Double_t g1 = par[3]*TMath::Exp(-0.5*e1*e1);
return g0+g1;
}
void scott()
{
// Create the original function
TF1 *g2 = new TF1("g2",g2,0,1,6);
g2->SetParameters(2,0.3,0.1, 1,0.7,0.15);
//Get random numbers from g2 function
TH1F *h1 = new TH1F("h1","Scott test",100,0,1);
h1->FillRandom("g2",10000);
//Draw h1 full
h1->SetFillColor(17);
h1->Draw();
//Copy h1 in a clone h1c. Set range and color for h1c
TH1F *h1c = (TH1F*)h1->Clone();
h1c->SetFillColor(42);
h1c->GetXaxis()->SetRange(50,90);
h1c->Draw("same");
//to draw a shaded area above and below an histogram range, we create
//a TGraph object (here we shade bins 60 to 80).
Int_t i;
Int_t n = 2*(80-60);
TGraph *gr = new TGraph(2*n);
for (i=0;i<20;i++) {
Float_t xlow = h1->GetBinLowEdge(60+i);
Float_t xup = h1->GetBinLowEdge(60+i+1);
Float_t y = h1->GetBinContent(60+i);
Float_t yup = 1.1*y;
Float_t ydown= 0.9*y;
gr->SetPoint(2*i, xlow,yup);
gr->SetPoint(2*i+1,xup, yup);
gr->SetPoint(2*n-2*i-1,xlow, ydown);
gr->SetPoint(2*n-2*i-2,xup, ydown);
}
gr->SetFillColor(2);
gr->Draw("lf");
}
This archive was generated by hypermail 2b29 : Tue Jan 04 2000 - 00:34:33 MET