Hello everybody,

I was experimenting with some functions useful in physics and learning to plot some. At one point, I decided to toy with f[x_]=Abs. Plotting gave the expected. I took the derivative of this function and then tried to plot it. No luck there... There is only the coordinate system while I had expected to see the usual "step" function. For negative numbers for x, the derivative should be -1 always, and plus one for positive x. Plot[Evaluate[D[f[x_], x_]], {x, -2, 2}] does not work. The command Plot[Evaluate[x/Abs], {x, -2, 2}] does give the expected plot.

I may be doing something very silly but or I came immediately across something pretty damn strange.

Thanks,

Patrick