$\left[\left[\mathrm{-5}\,5\right]\,\left[0\,2\right]\,\left[2\,\mathrm{-1}\right]\,\left[4\,0\right]\right]$

$\left[\left[-5\,5\right]\,\left[0\,2\right]\,\left[2\,-1\right]\,\left[4\,0\right]\right]$

$b:=\mathrm{CurveFitting}\left[\mathrm{BSplineCurve}\right]\left(\,v\right)$

$b:=\left[\&lcub;\begin{array}{cc}0& v<0\\ -\frac{5}{6}{v}^3& v<1\\ \frac{5}{3}-\frac{5}{2}v-\frac{5}{2}{\left(v-1\right)}^2\&plus;\frac{5}{2}{\left(v-1\right)}^3& v<2\\ -\frac{10}{3}\&plus;5{\left(v-2\right)}^2-\frac{13}{6}{\left(v-2\right)}^3& v<3\\ -11\&plus;\frac{7}{2}v-\frac{3}{2}{\left(v-3\right)}^2\&plus;\frac{1}{2}{\left(v-3\right)}^3& v<4\\ -6-{\left(v-4\right)}^3\&plus;2v& v<5\\ 8-v-3{\left(v-5\right)}^2\&plus;\frac{5}{3}{\left(v-5\right)}^3& v<6\\ \frac{38}{3}-2v\&plus;2{\left(v-6\right)}^2-\frac{2}{3}{\left(v-6\right)}^3& v<7\\ 0& 7\le v\end{array}\&comma;\&lcub;\begin{array}{cc}0& v<0\\ \frac{5}{6}{v}^3& v<1\\ -\frac{5}{3}\&plus;\frac{5}{2}v\&plus;\frac{5}{2}{\left(v-1\right)}^2-\frac{13}{6}{\left(v-1\right)}^3& v<2\\ \frac{5}{3}-4{\left(v-2\right)}^2\&plus;\frac{4}{3}{\left(v-2\right)}^3\&plus;v& v<3\\ 11-3v\&plus;\frac{2}{3}{\left(v-3\right)}^3& v<4\\ \frac{11}{3}-v\&plus;2{\left(v-4\right)}^2-\frac{5}{6}{\left(v-4\right)}^3& v<5\\ -\frac{8}{3}\&plus;\frac{1}{2}v-\frac{1}{2}{\left(v-5\right)}^2\&plus;\frac{1}{6}{\left(v-5\right)}^3& v<6\\ 0& 6\le v\end{array}\&comma;v\&equals;3..4\right]$