There are a lot of different representations possible for a lot of different purposes. So the answer might really depend. A clean way of doing it is to use SawtoothWave
This spends 3/4ths of it's time under 0:
SawtoothWave[x] - 3/4
This spends half of it's time under 0:
SawtoothWave[x] - 1/2
This spends a quarter of it's time under 0:
SawtoothWave[x] - 1/4
So you can use UnitStep[SawtoothWave[x] - p] where p is the proportion of the function that should be 0. If you want it expanded you can always divide x by how much you want the function stretched out by.