TITLE Sine wave with lag
: SCoP example of the use of the LAG directive.  lagwave
: is a delayed version of the sine function x.
: Simulation Resources, Inc.
: August 27, 1996
PARAMETER
{
  a = 1.                        : Amplitude
  delay = 2.    (sec)           : Delay time
}

INDEPENDENT
{
  time FROM 0 TO 20 WITH 200    (sec)
}

ASSIGNED
{
  lagwave FROM -1.5 TO 1.5
}

STATE
{
  x FROM -1.5 TO 1.5  START 1
  y FROM -1.5 TO 1.5
}

DERIVATIVE rates
{
  LAG x BY delay

  x' = a * y
  y' = - a * x
  lagwave = lag_x_delay
}

BREAKPOINT
{
  SOLVE rates
}

PLOT x, lagwave VS time