Extract first value of high density/low density vector

Question

I'm stuck with an easy task, I really hope someone could help me with this..

I have a vector with values close to each other and distinct gaps in between. What I need is this vector minimized to a vector with every first value of all high density series.

Example:

original_vector <- c(0.001,0.002,0.003,0.004,0.1001,0.1002,0.1003,0.1004,0.1005,
                     0.5003,0.5004)
wanted_vector <- c(0.001,0.1001,0.5003)

Does someone know how to convert the original vector into the wanted vector?

Thanks in advance!

Answer 1

You'll of course first need to define what you consider low vs. high density.

Assuming you can decide on a cutoff distance between consecutive elements, tol, below which two consecutive elements are considered to be densely packed, you could use something like this:

f <- function(x, tol) {
    x[tol < diff(c(-Inf, x))]
}


original_vector <- c(0.001,0.002,0.003,0.004,0.1001,0.1002,0.1003,0.1004,0.1005,
                     0.5003,0.5004)

f(original_vector, tol = 0.002)
# [1] 0.0010 0.1001 0.5003