/X 0 def

/show {

currentpoint pop

X sub 5 gt { ( ) print } if

dup print

systemdict /show get exec

currentpoint pop /X exch def

} def

Finding structure in multiple streams of data is an important problem. Consider the streams of data flowing from a robot's sensors, the monitors in an intensive care unit, or periodic measurements of various indicators of the health of the economy. There is clearly utility in determining how current and past values in those streams are related to future values.