Mean using For loop

[lrg52595]

I have been tasked with finding the number of arguments, the mean, and variance of a vector that a user inputs. So far I have been able to figure out how to check for the amount of arguments but i cannot figure how to do the variance. I know I have to use a for loop but im not sure how to do it. Any help would be nice.

 #include <iostream> 
#include <vector>

int main (int argc, char** argv) {
	float a;
	std::vector <float> v;
		std::cout << "Enter numbers\n";
		while(std::cin>>a){
			v.push_back(a);
		}
	

	for(std::vector<float>::iterator i=v.begin();i==v.end();++i){
		

	}
	
	std::cout<<"There were "<<v.size()<<" numbers.\n";
    for(float&i:v)
        ;
    float sum=0;
    for(int n : v)
        sum += n;
    
    std::cout<<"sum="<<sum<<"/n";
    
    float avg; 
    avg=sum/v.size();
    std::cout<<"The mean of these numbers is "<<avg<<"/n";
    
}

[rafae11]

http://www.cplusplus.com/forum/beginner/91285/