How to successively combine years and months using purrr

gistfile1.txt

Hi, 

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PROBLEM STATEMENT
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I want to generate URLS for each month for each year as follows:

[...]
https://s3.amazonaws.com/data/201611.csv.zip
https://s3.amazonaws.com/data/201612.csv.zip
https://s3.amazonaws.com/data/201701.csv.zip
https://s3.amazonaws.com/data/201702.csv.zip
[...]

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CODE
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Here is my attempt:

head.f.name = "https://s3.amazonaws.com/data/%sA"
tail.f.name = ".csv.zip"
v.i = str_pad(1:12,2,pad="0") 

map_chr(2015:2017, ~sprintf(head.f.name,.)) %>%
  map2_chr(v.i,~str_replace(.,"[:upper:]$") )


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ERROR 
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But I get an error:
Error: `.x` (3) and `.y` (12) are different lengths


Should not the smaller vector be recycled in this case.

I think the base R solution from @jennybc is the best way to go. However, just for variety sake, here's a possible approach using purrr:

library(purrr)
url <- "https://s3.amazonaws.com/data/%d%02d.csv.zip"

d <- cross2(2015:2016, 1:12)
map_chr(d, ~ sprintf(url, .[[1]], .[[2]]))
#>  [1] "https://s3.amazonaws.com/data/201501.csv.zip"
#>  [2] "https://s3.amazonaws.com/data/201601.csv.zip"
#>  [3] "https://s3.amazonaws.com/data/201502.csv.zip"
#>  [4] "https://s3.amazonaws.com/data/201602.csv.zip"
#>  ...