// Other examples of interpolations can be found here
import graph;
unitsize(1cm);

typedef real hermite(real);

hermite hermite(pair [] m, real [] d)
{/*DOC Retourne la fonction polynôme de Hermite
   passant par les points m(x_i,y_i) de nombre dérivée d_i en ce point.
   Return Hermite polynomial interpolation function
   passing by the points m (x_i, y_i) of derived number d_i in this point.
   DOC*/
  return new real(real x){
    int n=m.length;
    if (n != d.length) abort("Hermite: nombres de paramètres incorrectes.");
    real q,qk,s,y=0;
    for (int k=0; k<n ; ++k) {
      real q=1, qk=1, s=0;
      for (int j=0; j<n; ++j)
        {
          if (j!=k){
            q=q*(x-m[j].x)^2;
            qk=qk*(m[k].x-m[j].x)^2;
            s=s+1/(m[k].x-m[j].x);
          }
        }
      y=y+q/qk*(m[k].y+(x-m[k].x)*(d[k]-2*s*m[k].y));
    }
    return y;
  };
}

pair[] m;
real[] d;
int nbpt=5;
real xmin=-2pi,
  xmax=2pi,
  l=xmax-xmin,
  step=l/(nbpt+1);
for (int i=1; i<=nbpt; ++i)
  {
    real x=xmin+i*step;
    m.push((x,sin(x)));
    draw(m[m.length-1],linewidth(2mm));
    d.push(cos(x));
  }

xlimits(-2pi,2pi);
ylimits(-2,2);
xaxis("$x$",BottomTop,Ticks);
yaxis("$y$",LeftRight,Ticks);

draw(graph(sin,xmin,xmax),1mm+.8red,"$x\longmapsto{}\sin x$");
draw(graph(hermite(m,d),xmin,xmax),"$x\longmapsto{}H(x)$");

attach(legend(),point(10S),30S);

    
import graph;
size(10cm);

xaxis("$x$", -2*pi,2*pi, Arrow);
yaxis("$y$", -4,4, Arrow);

typedef real realfcn(real); // Define new type: real function of real

realfcn TPC(int n) { //Return Taylor polynomial (degrees 2*n) of cos
  return new real(real x) {
    return sum(sequence(new real(int m){return (-1)^m*x^(2*m)/gamma(2*m+1);}, n+1));
  };
}
draw(graph(cos,-2pi,2pi), linewidth(2bp), legend="$\cos$");

int n=6; // Number of curves
pen[] p={palered, lightred, red, blue, purple, green};
p.cyclic=true; // p[6]=p[0], p[7]=p[1], etc...

for (int i=0; i < n; ++i) {
  draw(graph(TPC(i),-2*pi,2*pi), bp+p[i], legend="$T_{"+(string)i+"}$");
}

xlimits(-2*pi,2*pi, Crop);
ylimits(-4,4, Crop);

attach(legend(linelength=3mm),point(E),5E);
shipout(bbox(Fill(lightgrey)));