1. A system for estimating a volume of activation using a set of electrical stimulation settings, the system comprising: a processor configured to: receive electric field data and the set of electrical stimulation settings for use with an implanted leadwire, the electric field data comprising, for each of a plurality of neural elements, a value of an activating function at one or more locations along the neural element; apply the electric field data and the set of electrical stimulation settings to a volume of activation estimation model to determine an activation status for each of the one of more locations for each of the neural elements, wherein the volume of activation estimation model either 1) does not use as input a plurality of sets of values of an electrical field at different points in time, 2) includes only linear equations generated based on observed functioning of a model that uses differential equations, or 3) does not use more than one differential equation; and output an indication of an estimated volume of activation corresponding to those locations of the neural elements for which the activation status is determined to be active.