plitude = bulkmotion(P,scale,direction,showplots)</b></p>
    <p> Compute amplitude of bulk motion waveform from a phase map. Use the mean
 phases of image slices (3rd dimension) to infer the bulk motion waveform
 (4th dimension) of the entire volume. Find the peak-to-peak amplitude of
 this wave.
 
 Usage:
 amplitude = bulkmotion(P,scale,direction,showplots)

 Inputs:
 P .......... Phase map (4 or 5D), where the dimensions are
              (X,Y,Z,time,[direction]) and units are radians
 scale ...... Conv