I have this problem:
I have a curve/figure on a sheet of graphpaper. Then I have to select points, read the x,y-values and label them $t_{0} = 1.0$ and $ t_{1}=2.0$ ect. I now have to obtain a table of $x(t)$ and a table of $y(t)$.Then I have to fit these functions by spline functions. Thus I have $x(t) = S(t)$ and $y(t) = S^{*}(t)$, which gives an approximate parametric representation of the curve/figure.
My question is:
Why should I have to fit them with two splines function? When in fact I just can fit the table of y(x) with one spline function?