Question

Say I have some ranges represented by start coordinates start<-c(1,2,3) and end coordiantes end<-c(4,5,4) ;ranges<-data.frame(start,end) How can I split this up into one length intervals?
i.e. I want

this

   starts ends
1      1    4
2      2    5
3      3    4  

to be transformed into this:

   starts ends
1      1    2      |
2      3    4     <-end of original first interval
3      2    3      |
4      4    5     <-end of original second interval
5      3    4     <-end of original third interval

right now I have a for loop iterating through the list and creating a sequence sequence that goes from start to end but this loop takes a very long time to execute for long lists of ranges.

Answer 1

You could try creating text for the vectors, parse-ing and eval-uating and then using a matrix to create the data.frame:

txt <- paste("c(",paste(ranges$start,ranges$end,sep=":",collapse=","),")",sep="")

> txt
[1] "c(1:4,2:5,3:4)"

vec <- eval(parse(text=txt))
> vec
 [1] 1 2 3 4 2 3 4 5 3 4

mat <- matrix(vec,ncol=2,byrow=T)
> data.frame(mat)
  X1 X2
1  1  2
2  3  4
3  2  3
4  4  5
5  3  4