Is there a handy base R or package function for collapsing, or interpolating, between any gaps for the integer values of a sequence of numbers? I've searched functions like dplyr::dense_rank but they don't do the trick in this case. The below code generates an example starting sequence of numbers in a single column (column = Grp):
> myDF <- data.frame(Grp = c(1,2.1,2.2,4.1,4.2,6.1,9))
> myDF
Grp
1 1.0
2 2.1
3 2.2
4 4.1
5 4.2
6 6.1
7 9.0
Here's how I would like to change the output; below I manually add values with a column to the right of each Grp row ("Collapse") explaining what I am trying to derive:
> myDF
Grp Collapse
1 1.0 Every sequence starts with 1 so leave Grp as is
2 2.1 Integer gap between rows 1-2 is <= 1 so leave Grp as is
3 2.2 Integer gap between rows 2-3 is <= 1 so leave Grp as is
4 3.0 Integer gap between original rows 3-4 is not <= 1 so fill in the gap with the seq integer
5 4.1 Integer gap between rows 4-5 is <= 1 so leave Grp as is
6 4.2 Integer gap between rows 5-6 is <= 1 so leave Grp as is
7 5.0 Integer gap between original rows 5-6 is not <= 1 so fill in the gap with the seq integer
8 6.1 Integer gap between row 7-8 is <= 1 so leave Grp as is
9 7.0 Integer gap between original rows 6-7 is not <= 1 so fill in the gap with the seq integer
10 8.0 Integer gap between original rows 6-7 is not <= 1 so fill in the gap with the seq integer
11 9.0 Integer gap between row 10-11 is <= 1 so leave Grp as is
You can do:
f <- floor(myDF$Grp)
s <- seq(min(f), max(f))
sort(c(myDF$Grp, s[!s %in% f]))
#[1] 1.0 2.1 2.2 3.0 4.1 4.2 5.0 6.1 7.0 8.0 9.0