r - Extract every n-th + x subsequent elements from a vector -


i create vector in each element n-th element plus x following elements of vector.

for example, if have vector a:

a <- c(1,2,3,4,5,6,7,8,9,10)

my new vector b should have elements

b <- c(1,2,5,6,9,10)

meaning first 2 elements, third 2 elements etc.

any appreciated!

logical indexing recycling this:

a <- c(1,2,3,4,5,6,7,8,9,10) a[c(t,t,f,f)] ## [1]  1  2  5  6  9 10

from comment question:

n <- 4 x <- 2 a[c(rep(t, n-x), rep(f,x))] ## [1]  1  2  5  6  9 10

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