Typically, the independent variable is on the x axis and the dependent is on the y. Most modern economists consider price independent, hence the axes are rever

Typically, the independent variable is on the x axis and the dependent is on the y. Most modern economists consider price independent, hence the axes are reversed. The convention was created by Alfred Marshall and everyone has stuck to it ever since. I don't think it matters, since neither variable is causal. The "inputs" of the function are actually the supply and demand curves themselves and the output is both price and quantity.