Generate a sequence of numbers with repeated intervals - r

Question

I am trying to create sequences of number of 6 cases, but with 144 cases intervals.
Like this one for example
c(1:6, 144:149, 288:293)
1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
How could I generate automatically such a sequence with
seq
or with another function ?

Answer 1

I find the sequence function to be helpful in this case. If you had your data in a structure like this:
(info <- data.frame(start=c(1, 144, 288), len=c(6, 6, 6)))
# start len
# 1 1 6
# 2 144 6
# 3 288 6
then you could do this in one line with:
sequence(info$len) + rep(info$start-1, info$len)
# [1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
Note that this solution works even if the sequences you're combining are different lengths.

Answer 2

Here's one approach:
unlist(lapply(c(0L,(1:2)*144L-1L),`+`,seq_len(6)))
# or...
unlist(lapply(c(1L,(1:2)*144L),function(x)seq(x,x+5)))
Here's a way I like a little better:
rep(c(0L,(1:2)*144L-1L),each=6) + seq_len(6)
Generalizing...
rlen <- 6L
rgap <- 144L
rnum <- 3L
starters <- c(0L,seq_len(rnum-1L)*rgap-1L)
rep(starters, each=rlen) + seq_len(rlen)
# or...
unlist(lapply(starters+1L,function(x)seq(x,x+rlen-1L)))

Answer 3

This can also be done using seq or seq.int
x = c(1, 144, 288)
c(sapply(x, function(y) seq.int(y, length.out = 6)))
#[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
As #Frank mentioned in the comments here is another way to achieve this using #josilber's data structure (This is useful particularly when there is a need of different sequence length for different intervals)
c(with(info, mapply(seq.int, start, length.out=len)))
#[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293

Answer 4

From R >= 4.0.0, you can now do this in one line with sequence:
sequence(c(6,6,6), from = c(1,144,288))
[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
The first argument, nvec, is the length of each sequence; the second, from, is the starting point for each sequence.
As a function, with n being the number of intervals you want:
f <- function(n) sequence(rep(6,n), from = c(1,144*1:(n-1)))
f(3)
[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293

Answer 5

I am using R 3.3.2. OSX 10.9.4
I tried:
a<-c() # stores expected sequence
f<-288 # starting number of final sub-sequence
it<-144 # interval
for (d in seq(0,f,by=it))
{
if (d==0)
{
d=1
}
a<-c(a, seq(d,d+5))
print(d)
}
print(a)
AND the expected sequence stores in a.
[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
And another try:
a<-c() # stores expected sequence
it<-144 # interval
lo<-4 # number of sub-sequences
for (d in seq(0,by=it, length.out = lo))
{
if (d==0)
{
d=1
}
a<-c(a, seq(d,d+5))
print(d)
}
print(a)
The result:
[1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293 432 433 434 435 436 437

Answer 6

I tackled this with cumsum function
seq_n <- 3 # number of sequences
rep(1:6, seq_n) + rep(c(0, cumsum(rep(144, seq_n-1))-1), each = 6)
# [1] 1 2 3 4 5 6 144 145 146 147 148 149 288 289 290 291 292 293
No need to calculate starting values of sequences as in the #josilber's solution, but the length of a sequence has to be constant.