How to get Manipulate to work with FourierSeries Plot

Question

I have been trying to use Manipulate in the following expression :

Manipulate[
  Plot[
    Evaluate[
      FourierSeries[
        Piecewise[{
          {0, x < 0}, {1, (0 <= x <= 1)},
          {0, 1 < x }
        }], x, y
      ]
    ], {x, -2, +3}
  ], 
  {y, 1, 15}
]

When I press "evaluate notebook" it gives the y=1 plot, but moving the slider creates a blank plot.

Any help would be greatly appreciated.

Answer 1

What you call y is n as in the nth order Fourier series. If you don't use a step size, then the command fails. Actually, your code works. Try open the value box for y on the manipulate and enter 2 or another integer in range instead of dragging the slider.

---

Or specify an integer step as follows:

Manipulate[
 Plot[Evaluate[
   FourierSeries[
    Piecewise[{{0, x < 0}, {1, (0 <= x <= 1)}, {0, 1 < x}}], x, 
    y]], {x, -2, +3}], {y, 1, 15, 1}]