Examples

The following script demonstrates how you can use the FILTER command to smooth data. See Figure 1.

 X=[0:4:.05]
 Y=X^2-3*X+3+SIN(X*3)*RAN(X)*2
 WINDOW 5
 GRAPH\AXESONLY X Y
 GET XMIN XMIN
 GET XMAX XMAX
 GET YMIN YMIN
 GET YMAX YMAX
 SCALES XMIN XMAX YMIN YMAX
 SET PLOTSYMBOL -1
 GRAPH\OVERLAY X Y
 SET PLOTSYMBOL 0
 WINDOW 6
 FILTER\-RECURSIVE Y YF [-36;9;44;69;84;89;84;69;44;9;-36]
 SCALES XMIN XMAX YMIN YMAX
 GRAPH X YF/429
 WINDOW 7
 FILTER\-RECURSIVE Y YF [18;-45;-10;60;120;143;120;60;-10;-45;18]
 SCALES XMIN XMAX YMIN YMAX
 GRAPH X YF/429
 WINDOW 8
 FILTER\-RECURSIVE Y YF [-3;-6;-5;3;21;46;67;74;67;46;21;3;-5;-6;-3]
 SCALES XMIN XMAX YMIN YMAX
 GRAPH X YF/320
 

Fig. 1:   A FILTER example showing data smoothing

The following script demonstrates how you can use the FILTER command to differentiate data. See Figure 2.

 X=[0:4:.2]
 H=X[2]-X[1]
 Y=X^2-3*X+3
 WINDOW 5
 SET PLOTSYMBOL -1
 GRAPH X Y
 WINDOW 7
 SET PLOTSYMBOL 0
 FILTER\-RECURSIVE Y YF [-4;30;-120;40;60;-6]
 SCALES 0 4 -3 5
 SET PLOTSYMBOL -2
 GRAPH X YF/(120*H)
 SET PLOTSYMBOL 0
 GRAPH\OVERLAY X 2*X-3
 

Fig. 2:   A FILTER example showing the first derivative

  Recursive filters