In mathematics, a boxcar function is any function which is zero over the entire real line except for a single interval where it is equal to a constant, A. The boxcar function can be expressed in terms of the uniform distribution as where is the uniform distribution of x for the interval and is the Heaviside step function. As with most such discontinuous functions, there is a question of the value at the transition points. These values are probably best chosen for each individual application. When a boxcar function is selected as the impulse response of a filter, the result is a moving average filter. The function is named after its graph's resemblance to a boxcar, a type of railroad car. See also Boxcar averager Rectangular function Step function Top-hat filter References Special functions