Overshoot

Typical approach is to look at the Root Mean Squares (RMS), something like: where

• f(x) is say your fitted function
• g(x) are your original points

Obviously you select values of x that are at know points in g(x) and apply to f(x).

Consider this example

double f[4]={1,2,3,4};      // approx values (say)
  double g[4]={1.1,2,2.9,4};  // real values
 
  double RMS=0;
  for(int i=0;i<4;i++) RMS+=pow(f[i]-g[i],2);
  RMS=sqrt(RMS/4.0);