certain animal aggregations has been widely discussed (3). RCD may also be 

 computed by a sequence of simple arithematic operations as follows: 



(a) *SPLIT BUGS.PA BUGS.X BUGS.Y 



(b) *CDIF BUGS.X BUGS.DX 



(c) *CDIF BUGS.Y BUGS.DY 



(d) UCTAN BUGS.DX BUGS.DY BUGS.DI 



(e) *CDIF BUGS.DI BUGS.AC 



(0 *MULT/CO BUGS.AC BUGS.AV nl 

 (g) *ABSV BUGS.AV BUGS.RD 



Where "CDIF" is the CENTRAL DIFFERENCE operator (a discrete 

 approximation to the differential operator), "CTAN" is the CONTINUOUS 

 ARCTANGENT operator. "MULT/CO" denotes multipHcation by a constant 

 and "ABSV" is the ABSOLUTE VALUE operator. The resultant "BUGS.DI" 

 of step (d) is the direction of travel measured in degrees with respect to the 

 Bugsystem reference frame; it could have been generated from the original path 

 data using the DIRECTION OF TRAVEL operator. Tlie resultant "BUGS.AV" 

 of step (f) contains angular velocities (measured in degrees per second); this file 

 could have been produced using the ANGULAR VELOCITY operator. Other 

 operators have been developed to evaluate LINEAR VELOCITY and NET TO 

 GROSS DISPLACEMENT RATIO functions defined upon path data. 



Simple Statistical Processing 



For the purpose of statistical analysis two different types of data 

 structure— representing two levels in a structural hierarchy— may be 

 distinguished as "samples": vectors and files. Many statistical operators 

 recognize this distinction. For example the STATISTICAL PARAMETER 

 operator estimates parameters such as the mean, variance, standard deviation, 

 skewness, kurtosis, etc. The command 



*STAT/VE BUGS.LV BUGS.ST 



produces the resultant file "BUGS.ST', containing one data vector (i.e., a list 

 of statistical parameters) for each data vector in the operand, whereas the 

 command 



*STAT/FI BUGS.LV BUGS.ST 



produces only one resultant data vector characterizing the entire file. In either 

 case, the user can LIST the resultant parameters. Similarly, the SLOT operator 

 provides for estimation of density and distribution functions via histograms 

 both for individual vectors and entire files. These data may be displayed 

 graphically (Figure 17-3) or LISTed on the terminal or the line printer. 



267 



