涉及根函数和事件函数的终结ODE求解器

Question

我出于说明目的从文档中提取了此示例。在以下示例中，当y的值达到0.1时，将添加一个随机值。如果y值大于0.8，我想终止求解器。

一种可能的解决方案是在eventfun中生成随机值，以使y始终小于0.8。还有其他解决方案可以终止求解器？这对我的复杂模型很有帮助。

## =======================================================================
## Example 3:
##   using lsodar to trigger an event
## =======================================================================

## a state variable is decaying at a first-order rate. 
## when it reaches the value 0.1, a random amount is added.
library("deSolve")

derivfun <- function (t,y,parms)
  list (-0.05 * y)

rootfun <- function (t,y,parms)
  return(y - 0.1) 

eventfun <- function(t,y,parms)
  return(y + runif(1))  


yini <- 0.5
times <- 0:400

out <- lsodar(func=derivfun, y = yini, times=times, 
              rootfunc = rootfun, events = list(func=eventfun, root = TRUE))

plot(out, type = "l", lwd = 2, main = "lsodar with event")

# }