How to calculate time spent below a threshold?

Question

I have a plot with time as a PosixCt object on the x-axis and a dependent variable "ODBA" on the y-axis . The experiment was a 600-second trial. How do I calculate the total time in seconds that ODBA was below a certain threshold (eg 0.25) ?

Answer 1

We can use sum

sum(as.numeric(format(time, "%S"))[ODBA > 0.25])