  A memristor is often identified by showing its distinctive pinched hysteresis
curve and testing for the effect of frequency. The hysteresis size should
relate to frequency and shrink to zero as the frequency approaches infinity.
Although mathematically understood, the material causes for this are not well
known. The d.c. response of the memristor is a decaying curve with its own
timescale. We show via mathematical reasoning that this decaying curve when
transformed to a.c. leads to the frequency effect by considering a descretized
curve. We then demonstrate the validity of this approach with experimental data
from two different types of memristors.
