How can I plot with Mathematica, Muller's example:
$f(t,x) = \begin{cases} 0 & t \leq 0, x \in \mathbb{R} \\ 2t & t>0,x < 0 \\ 2t - \frac{4x}{t} & t >0,0 \leq x \leq t^2 \\ -2t & t>0,x > t^2 \, . \end{cases}$
which is a piecewise function of two variables?
Other examples
Plot a parametric function from $\mathbb{R}^2$ to $\mathbb{R}^2$
Piecewise
in the documentation?... $\endgroup$ – José Antonio Díaz Navas Mar 25 '18 at 11:25f[x_, t_] := Piecewise[{{0, t <= 0}, {2 t, t > 0 && x < 0}, {2 t - 4 x/t, t > 0 && 0 <= x <= t^2}, {-2 t, t > 0 && x > t^2}}]
andPlot3D
... $\endgroup$ – José Antonio Díaz Navas Mar 25 '18 at 11:35