C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  code to find correlation          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Gary Wessle Guest Posted: Sun Aug 27, 2006 3:31 am    Post subject: code to find correlation Hi I wrote a code to calculate the correlation between 2 sequence of double numbers presented as vectors. did I go about this the right way? thanks #include <vector> using std::vector; #include <valarray> using std::valarray; cor::cor(vector<double>& x, vector<double>& y) { int c = x.size(); int d = y.size(); if(c != d) cout << "to calculate correlation, variables" " must be of the same number of elements" << endl; // converts the input to valarray for spead and ellegance. valarray<double> a(c); valarray<double> b(d); copy(x.begin(), x.end(), &a[0]); copy(y.begin(), y.end(), &b[0]); // expected values "mean" double Ea = a.sum() / static_cast<double> (a.size()); double Eb = b.sum() / static_cast<double> (b.size()); // standard diviation double Sa = sqrt( pow((a-Ea),2).sum()/c ); double Sb = sqrt( pow((b-Eb),2).sum()/d ); // double Sb = sqrt( ((a*a).sum()/c)- pow(Ea, 2) ); // faster // but more round-offs // correlation cof = ( ((a-Ea)/Sa)*((b-Eb)/Sb) ).sum()/(c-1); } Back to top Victor Bazarov Guest Posted: Sun Aug 27, 2006 7:51 am    Post subject: Re: code to find correlation Gary Wessle wrote: Quote: I wrote a code to calculate the correlation between 2 sequence of double numbers presented as vectors. did I go about this the right way? I would never use 'cout' in a constructor unless it's a debug output (in that case it should go to 'cerr' and be #ifdef'ed). You might think of throwing an exception instead. Quote: thanks #include <vector using std::vector; #include <valarray using std::valarray; cor::cor(vector<double>& x, vector<double>& y) { int c = x.size(); int d = y.size(); if(c != d) cout << "to calculate correlation, variables" " must be of the same number of elements" << endl; // converts the input to valarray for spead and ellegance. valarray<double> a(c); valarray<double> b(d); copy(x.begin(), x.end(), &a[0]); copy(y.begin(), y.end(), &b[0]); // expected values "mean" double Ea = a.sum() / static_cast<double> (a.size()); double Eb = b.sum() / static_cast<double> (b.size()); // standard diviation Isn't it "deviation"? Quote: double Sa = sqrt( pow((a-Ea),2).sum()/c ); double Sb = sqrt( pow((b-Eb),2).sum()/d ); What are the extra parentheses aroud 'x-Ex' for? Quote: // double Sb = sqrt( ((a*a).sum()/c)- pow(Ea, 2) ); // faster // but more round-offs // correlation cof = ( ((a-Ea)/Sa)*((b-Eb)/Sb) ).sum()/(c-1); } Well, I see 'cor' is an object. Why? Does it have states? Does it have a life on its own? What's the reason for it to be an object? Shouldn't you simply have a function, like double cor(vector..., vector...) { ... return cof; } ? V -- Please remove capital 'A's when replying by e-mail I do not respond to top-posted replies, please don't ask Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.