LinearData.cpp

//
//  LinearData.cpp
//  projet
//
//  Created by Etienne Dejoie on 05/01/2016.
//
//


using namespace std;

class LinearRansac : public Data<pair<float, float> >{
    
    public:
        vector<pair<float, float> > vc;
    
    int minEstNb = 2;
    int nbParameters = 2;
    
    LinearRansac (vector<float> source, vector<float> target){
        
        if (source.size() != target.size()) {
            cout << "la taille de target est différente de celle de source, problème" << endl;
        }
        else {
            for (int i = 0 ; i < source.size(); i++) {
                vc.push_back(make_pair(source[i], target[i]));
            }
            
        }
    }
    
  
    vector<float> estimModel(vector<pair<float, float> > ll){
        
        int n = ll.size();
        
        // calculate the averages of arrays x and y
        float xa = 0, ya = 0;
        for (int i = 0; i < n; i++) {
            xa += ll[i].first;
            ya += ll[i].second;
        }
        xa /= n;
        ya /= n;
        
        // calculate auxiliary sums
        float xx = 0, yy = 0, xy = 0;
        for (int i = 0; i < n; i++) {
            float tmpx = ll[i].first- xa, tmpy = ll[i].second - ya;
            xx += tmpx * tmpx;
            yy += tmpy * tmpy;
            xy += tmpx * tmpy;
        }
        
        // calculate regression line parameters
        
        
        float m_b = xy / xx;
        float m_a = ya - m_b * xa;
        
        vector<float> params;
        params.push_back(m_b);
        params.push_back(m_a);
        
        return params;//return slope, intercept
    }
    
    float calculateError(pair<float, float> d, vector<float> model){
        return pow(d.second - model[0]*d.first - model[1], 2);
        
    }
    
    float calculateError(vector<pair<float,float> > dat, vector<float> model){
        
        float S = 0;
        int n = dat.size();
        
        for(pair<float,float> p : dat)
            S += calculateError(p, model);
        
        return S/n;
        
    }
    
};