Re: Re: TH2D::Integral()

You had two problems - The double counting is for the reasons Mario suggested.

The value 0.5 falls into the 0.50->0.51 bin, and so when you set to the range 0,0.5 you are actually taking bins 1->51. If you plot the histogram and try to scale the axis from 0 to 0.5, you will see it actually refuses to cut off a bin and so instead draws 0->0.51.

To fix this, you either want to take the range 0->0.4999...., or, perhaps better, calculate the integral on bin range ie box2 = h2->Integral(0, 50, 51, 101);

which also takes into account the overflow bins (if you wanted!).

Nick

On Jun 2, 2009 2:36pm, Anil Singh <anil79_at_fnal.gov> wrote:
> Mario,

> yeah, there was a typo actually this was just a

> dummy created to reproduce my problem. I corrected

> and had a re run:

> //-----

> Full Integral: 10000

> Box1: 2655

> Box2: 2556

> Box3: 2535

> Box4: 2439

> Sum of all Boxes: 10185

> //----

> So as you say, there still may be some double counting.

> Is there some easy way to correct this ??

> Anil

> ----- Original Message -----

> From: Mario Kadastik mario.kadastik_at_cern.ch>

> Date: Tuesday, June 2, 2009 6:59 pm

> Subject: Re: [ROOT] TH2D::Integral()

> To: Mario Kadastik mario.kadastik_at_cern.ch>

> Cc: Anil Singh anil79_at_fnal.gov>, roottalk_at_pcroot.cern.ch

> > >> // Box1

> > >> float box1=BoxIntegral(h2,0,x_cut,0,y_cut);

> > >>

> > >> //Box2

> > >> float box2=BoxIntegral(h2,0,x_cut,y_cut,1);

> > >>

> > >> //Box3

> > >> float box3=BoxIntegral(h2,x_cut,1,0,y_cut);

> > >>

> > >> //Box4

> > >> float box4=BoxIntegral(h2,x_cut,1,0,y_cut);

> > >

> > > Aren't you taking a small overlap in the region where x_cut and

> > > y_cut lines overlap? I'd guess that if you exclude the overlap

> > > region you could well end up with the right result. Though the 25%

> >

> > > increase is a bit more than I'd have expected from the overlap in

> > > case of 100 x 100 matrix.

> >

> > Ehh ... it's even simpler :) You have a typo. Your Box3 and Box4 are

> >

> > identical regions. You should be integrating from y_cut to 1 in Box4

> >

> > to cover the whole range.

> >

> > Mario

> >
Received on Tue Jun 02 2009 - 15:42:56 CEST