Calculate cycle time for a signal by code

I want to calculate the cycle time for a signal (the frequency) by using a code (Matlab function block). For examble, in a motor rotor position the angle changes between 0 and 360 degrees, so the time between two identical values (cycle time) is needed to be calculated

[Benjamin Thompson]

Need more information. Are you measuring motor speed, or does the motor actually change direction? fft is one way to measure and find a dominant frequency in a signal.