# Tf2

Hi ROOTers
i have a problem on TF2.i have some histogram and i want to calculate the following equation and summation.
my equations are N11 = Nsm + 0.01alpha + 0.01beta, N21 = Nsm + 0.02alpha + 0.01beta that i can obtain alpha and beta here .alpha=(N21-N11)/0.01, beta=(2*N11-N21-Nsm)/0.01;
so i want to calculate this summation = ((N11-Nsm)/Nsm)^2 that from i=0 to i=20 and i defined the Nsm,N11,N21 by this form:

int Nsm=hz->GetBinContent(is);

int N11=hz11->GetBinContent(is);

int N21=hz21->GetBinContent(is);
the part of my code is:
for(int is = 0 ; is < 20; is++)
{

int Nsm=hz->GetBinContent(is);

int N11=hz11->GetBinContent(is);

int N21=hz21->GetBinContent(is);

// N11 = Nsm + 0.01alpha + 0.01beta;
// N21 = Nsm + 0.02alpha + 0.01beta;

int alpha=(N21-N11)/0.01;
int beta=(2*N11-N21-Nsm)/0.01;

ki2 = ???((alphax+betay)/Nsm)^2
//??? i don’t know summation script on C++
}

i don’t know how calculate summation and draw TF2 function.ki2 is function that plce on the TF2 and ki2 should be draw in term of x,y.
best regards

Hi,

how and where are x, y, and ki2 defined? Do you have a complete and running script that does everything but the summation of ki2 and the drawing? That might make it easier to understand what you are trying to do.

Cheers, Axel.

Hi,ALEX,

i searched and find some way for this problem and correct past code but i have another problem.
code is :
for(int is = 0 ; is < 20; is++)
{
int Nsm=hz->GetBinContent(is);
int N11=hz11->GetBinContent(is);
int N21=hz21->GetBinContent(is);
// N11=Nsm+0.01alpha+0.01beta;
// N21=Nsm+0.02alpha+0.01beta;
int alpha=(N21-N11)/0.01;
int beta=(2*N11-N21-Nsm)/0.01;

[color=red]now here i want to sum .i want to calculate coefficients but i can’t.i think i can not writing a loop or script to calculate for this summation.if i can calculate a,b,c my workis finish.

are these below lines true?
? int a=a+(alpha^2/Nsm);
?int b=b+(beta^2/Nsm);
?int c=c+((alpha*beta)/Nsm);[/color]
}

TF2 *ki2 = new TF2(“ki2”,"[0]*x^2+[1]*y^2+[2]xy",-1,1,-1,1);
ki2->SetParameters(0,a);
ki2->SetParameters(1,b);
ki2->SetParameters(2,c);
ki2->Draw();

thanks for your attention,i apology you beacuse i was bother you.

Hi,

you don’t bother me at all You should (re-) read the part on scopes in your C++ book; a, b and c need to be declared outside the loop. And instead of a = a + whatever you can simply write a+= whatever. Really - if you don’t know the basics of C++ you will not be able to use ROOT, so please make sure you have read an introduction to C++.

Cheers, Axel.