Event Detection in ODE solution
Detect events in solutions of a differential equation.
deeve(x, y, yv = 0, idx = NULL)
x |
vector of (time) points at which the differential equation has been solved. |
y |
values of the function(s) that have been computed for the given (time) points. |
yv |
point or numeric vector at which the solution is wanted. |
idx |
index of functions whose vales shall be returned. |
Determines when (in x coordinates) the idx-th solution
function will take on the value yv.
The interpolation is linear for the moment. For points outside the
x interval NA is returned.
A (time) point x0 at which the event happens.
The interpolation is linear only for the moment.
## Damped pendulum: y'' = -0.3 y' - sin(y)
# y1 = y, y2 = y': y1' = y2, y2' = -0.3*y2 - sin(y1)
f <- function(t, y) {
dy1 <- y[2]
dy2 <- -0.3*y[2] - sin(y[1])
return(c(dy1, dy2))
}
sol <- rk4sys(f, 0, 10, c(pi/2, 0), 100)
deeve(sol$x, sol$y[,1]) # y1 = 0 : elongation in [sec]
# [1] 2.073507 5.414753 8.650250
# matplot(sol$x, sol$y); grid()Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.