Sequence of months
Examples
ym_seq(201303, 201512)
#> [1] 201303 201304 201305 201306 201307 201308 201309 201310 201311 201312
#> [11] 201401 201402 201403 201404 201405 201406 201407 201408 201409 201410
#> [21] 201411 201412 201501 201502 201503 201504 201505 201506 201507 201508
#> [31] 201509 201510 201511 201512