cleanEventTimes: Find Nearest Event for Each Time Step and Clean Time Steps to Avoid Doubles

Description

These functions can be used for checking time steps and events used by ode solver functions. They are normally called internally within the solvers.

Usage

nearestEvent(times, eventtimes)
cleanEventTimes(times, eventtimes, eps = .Machine$double.eps * 10)

Arguments

times

the vector of output times,

eventtimes

a vector with the event times,

eps

relative tolerance value below which two numbers are assumed to be numerically equal.

Value

nearestEvent returns a vector with the closest events for each time step and

cleanEventTimes returns a vector with the output times without all those that are 'very close' to an event.

Details

In floating point arithmetics, problems can occur if values have to be compared for 'equality' but are only close to each other and not exactly the same.

The utility functions can be used to add all eventtimes to the output times vector, but without including times that are very close to an event.

This means that all values of eventtimes are contained but only the subset of times that have no close neighbors in eventtimes.

These checks are normally performed internally by the integration solvers.

Examples

Run this code

# NOT RUN {
events <- sort(c(0, 2, 3, 4 + 1e-10, 5, 7 - 1e-10,
                 7 + 6e-15, 7.5, 9, 24.9999, 25, 80, 1001, 1e300))
times  <- sort(c(0, 1:7, 4.5, 6.75, 7.5, 9.2, 9.0001, 25, 879, 1e3, 1e300+5))

nearest <- nearestEvent(times, events)
data.frame(times=times, nearest = nearest)

## typical usage: include all events in times after removing values that
## are numerically close together, events have priority 
times
unique_times <- cleanEventTimes(times, events)
newtimes <- sort(c(unique_times, events))
newtimes
# }