Question

I wrote this code for smoothing of a curve .
It takes 5 points next to a point and adds them and averages it .

/* Smoothing */
void smoothing(vector<Point2D> &a)
{
    //How many neighbours to smooth
    int NO_OF_NEIGHBOURS=10;
    vector<Point2D> tmp=a;
    for(int i=0;i<a.size();i++)
    {

        if(i+NO_OF_NEIGHBOURS+1<a.size())
        {
            for(int j=1;j<NO_OF_NEIGHBOURS;j++)
            {
                a.at(i).x+=a.at(i+j).x;
                a.at(i).y+=a.at(i+j).y;
            }
            a.at(i).x/=NO_OF_NEIGHBOURS;
            a.at(i).y/=NO_OF_NEIGHBOURS;

        }
        else
        {
            for(int j=1;j<NO_OF_NEIGHBOURS;j++)
            {
                a.at(i).x+=tmp.at(i-j).x;
                a.at(i).y+=tmp.at(i-j).y;
            }
            a.at(i).x/=NO_OF_NEIGHBOURS;
            a.at(i).y/=NO_OF_NEIGHBOURS;
        }

    }

}

But i get very high values for each point, instead of the similar values to the previous point . The shape is maximized a lot , what is going wrong in this algorithm ?

Answer 1

in following block:

            for(int j=0;j<NO_OF_NEIGHBOURS;j++)
            {
                a.at(i).x=a.at(i).x+a.at(i+j).x;
                a.at(i).y=a.at(i).y+a.at(i+j).y;
            }

for each neighbour you add a.at(i)’s x and y respectively to neighbour values.

i understand correctly, it should be something like this.

            for(int j=0;j<NO_OF_NEIGHBOURS;j++)
            {
                a.at(i).x += a.at(i+j+1).x
                a.at(i).y += a.at(i+j+1).y
            }