vagabond vagabond - 2 months ago 7
R Question

repeat a vector up to the nth element

The vector i want to repeat is :

> months2014
[1] "07" "08" "09" "10" "11" "12"


I want to repeat it based on this vector which defines the nth values:

> num_times
[1] 6 6 6 6 5 6 6 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
[33] 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 12 6 6 6 6 6 6 6 12 6 6 6 6 6 6
[65] 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 12 6
[97] 6 6 12 6 6 6 6 6 6 6 6 12 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 2 6 6
[129] 6 12 6 6 6 6 6 6


I used this loop to get the below output:

for (i in num_times)
print(months2014[1:i])

[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" ## repeated upto the 5th element
[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" "12"
[1] "07" "08" "09" "10" "11" ## repeated up to the 6th element


If you look at the num_times vector, it also has 12. Because of this I also get this result:

[1] "07" "08" "09" "10" "11" "12" NA NA NA NA NA NA


There are only 6 elements in
months2014
so I get NAs. I actually want it to restart and get output like this:

[1] "07" "08" "09" "10" "11" "12" "07 "08" "09" "10" "11" "12"


I have three questions:

1) How do I save the loop output? I tried creating an empty vector and putting the results into it but that didn't work:

temp_vec <- c()
for (i in num_times)
temp_vec <- print(months2014[1:i])


2) How do I fix the NA ?

3) There must be a better way of doing this?

Answer

After testing this seems to work:

sapply(num_times,function(x) rep(months2014,length.out=x)

It outputs a list and repeats the sequence if the value in num_times is higher than the length of months214:

[[1]]
[1] "07" "08" "09" "10" "11" "12"

[[2]]
[1] "07" "08" "09" "10" "11" "12"

[[3]]
[1] "07" "08" "09" "10" "11" "12"

[[4]]
[1] "07" "08" "09" "10" "11" "12"

[[5]]
[1] "07" "08" "09" "10" "11"

[[6]]
 [1] "07" "08" "09" "10" "11" "12" "07" "08" "09" "10" "11" "12"