# Filling the area between two curves

Hi ,
I am trying to fill the area between two TGraph objects. The SetFillColor option is not solving this problem. I also tried using the example for drawing exclusion region, but since this draws bands of fixed size this doesn’t help me.
-thanks Debdatta.

see example below:

Rene

``````void grshade() {
TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);

c1->SetGrid();
c1->DrawFrame(0,0,2.2,12);

const Int_t n = 20;
Double_t x[n], y[n],ymin[n], ymax[n];
Int_t i;
for (i=0;i<n;i++) {
x[i] = 0.1+i*0.1;
ymax[i] = 10*sin(x[i]+0.2);
ymin[i] = 8*sin(x[i]+0.1);
y[i] = 9*sin(x[i]+0.15);
}
TGraph *grmin = new TGraph(n,x,ymin);
TGraph *grmax = new TGraph(n,x,ymax);
TGraph *gr    = new TGraph(n,x,y);
for (i=0;i<n;i++) {
}
grmin->Draw("l");
grmax->Draw("l");
gr->SetLineWidth(4);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(21);
gr->Draw("CP");
}
``````

Hello Rene,
thanks , this is what I was looking for.

Hi,
Is there anyway to set the transparency of the coloured area when it is “solid” filled?

I tried this two things (one is commented) but none works:

``````void grshade() {
TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);

c1->SetGrid();
c1->DrawFrame(0,0,2.2,12);

const Int_t n = 20;
Double_t x[n], y[n],ymin[n], ymax[n];
Int_t i;
for (i=0;i<n;i++) {
x[i] = 0.1+i*0.1;
ymax[i] = 10*sin(x[i]+0.2);
ymin[i] = 8*sin(x[i]+0.1);
y[i] = 9*sin(x[i]+0.15);
}
TGraph *grmin = new TGraph(n,x,ymin);
TGraph *grmax = new TGraph(n,x,ymax);
TGraph *gr    = new TGraph(n,x,y);
for (i=0;i<n;i++) {
}
/*
TColor *col26 = gROOT->GetColor(26);
col26->SetAlpha(0.2);
*/
grmin->Draw("l");
grmax->Draw("l");
gr->SetLineWidth(4);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(21);
gr->Draw("CP");
}
``````

I always get an opaque color

See at the end of the transparency doc:

The transparency is available on all platforms when the flag `OpenGL.CanvasPreferGL` is set to `1` in `\$ROOTSYS/etc/system.rootrc` , or on Mac with the Cocoa backend. On the file output it is visible with PDF, PNG, Gif, JPEG, SVG, TeX … but not PostScript.

I don’t really know if I did it right but still it doesn’t work. I edited the file `D:\Debian\ROOT\etc\system.rootrc` (where I installed ROOT) to have

``````# Flag to set CanvasPreferGL via gStyle
OpenGL.CanvasPreferGL:                      1
``````

I run the code again (in a new console), but nothing changes.

I’m using Windows Subsystem for Linux (Debian):
ROOT 6.24/06
Built for linuxx8664gcc

Yes it works on my Mac where transparency on-screen is supported:

``````void grshade() {
TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);

c1->SetGrid();
c1->DrawFrame(0,0,2.2,12);

const Int_t n = 20;
Double_t x[n], y[n],ymin[n], ymax[n];
Int_t i;
for (i=0;i<n;i++) {
x[i] = 0.1+i*0.1;
ymax[i] = 10*sin(x[i]+0.2);
ymin[i] = 8*sin(x[i]+0.1);
y[i] = 9*sin(x[i]+0.15);
}
TGraph *grmin = new TGraph(n,x,ymin);
TGraph *grmax = new TGraph(n,x,ymax);
TGraph *gr    = new TGraph(n,x,y);
for (i=0;i<n;i++) {
}
grmin->Draw("l");
grmax->Draw("l");
gr->SetLineWidth(4);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(21);
gr->Draw("CP");
}
``````

``````gStyle->SetCanvasPreferGL(true);