Fig. 3. The velocity of each cell was analyzed in regard to speed and trajectory. Examples show four types of analysis for four cells cultured from G. mirabilis, two moving in straight lines and two moving in circles: (A) a trajectory plot of (x,y) coordinates of the positions of four cells over 20 min, beginning at the origin and rotated such that the first step is along the y-axis (x=0); (B) speed histograms of the frequency of instantaneous cell speeds; (C) autocorrelation analysis of cell speed shows memory (correlation) and oscillation; and (D) cosine analysis shows the magnitude of turning angles () made by the cell over time.