Issue with unitroot_nsdiffs with NA values

[mitchelloharawild]

library(tsibble)
library(tidyverse)
library(feasts)
#> Loading required package: fablelite
#> 
#> Attaching package: 'feasts'
#> The following object is masked from 'package:grDevices':
#> 
#>     X11
AirPass <- as_tsibble(AirPassengers) %>% rename(month = index, pass = value)

## test for seasonal differencing first
AirPass %>% 
  features(log(pass), unitroot_nsdiffs)   # reports minimum seasonal differences = 1
#> # A tibble: 1 x 1
#>   nsdiffs
#>     <int>
#> 1       1
## perform one seasonal differencing and then test for first differencing
AirPass %>% 
  mutate(SDpass = difference(log(pass), lag = 12)) %>%
  features(SDpass, unitroot_ndiffs)     # reports minimum first differences = 0
#> # A tibble: 1 x 1
#>   ndiffs
#>    <int>
#> 1      0

## if you test for first differencing first
AirPass %>% 
  features(log(pass), unitroot_ndiffs)    # reports minimum first differences = 1
#> # A tibble: 1 x 1
#>   ndiffs
#>    <int>
#> 1      1
## perform a first differencing and then test for seasonal differencing
AirPass %>% 
  mutate(Dpass = difference(log(pass), lag = 1)) %>%
  features(Dpass, unitroot_nsdiffs)      # the output is just a blank row
#> # A tibble: 1 x 0

## If I filter out the NA in the first row from the first differencing…
AirPass %>% 
  mutate(Dpass = difference(log(pass), lag = 1)) %>%
  slice(2:nrow(AirPass)) %>% 
  features(Dpass, unitroot_nsdiffs)    # reports minimum seasonal differences = 1
#> # A tibble: 1 x 1
#>   nsdiffs
#>     <int>
#> 1       1

^{Created on 2019-07-17 by the reprex package (v0.3.0)}

[mitchelloharawild]

Should work fine now.

library(tsibble)
library(tidyverse)
library(feasts)
#> Loading required package: fablelite
AirPass <- as_tsibble(AirPassengers) %>% rename(month = index, pass = value)

## test for seasonal differencing first
AirPass %>% 
  features(log(pass), unitroot_nsdiffs)   # reports minimum seasonal differences = 1
#> # A tibble: 1 x 1
#>   nsdiffs
#>     <int>
#> 1       1
## perform one seasonal differencing and then test for first differencing
AirPass %>% 
  mutate(SDpass = difference(log(pass), lag = 12)) %>%
  features(SDpass, unitroot_ndiffs)     # reports minimum first differences = 0
#> # A tibble: 1 x 1
#>   ndiffs
#>    <int>
#> 1      0

## if you test for first differencing first
AirPass %>% 
  features(log(pass), unitroot_ndiffs)    # reports minimum first differences = 1
#> # A tibble: 1 x 1
#>   ndiffs
#>    <int>
#> 1      1
## perform a first differencing and then test for seasonal differencing
AirPass %>% 
  mutate(Dpass = difference(log(pass), lag = 1)) %>%
  features(Dpass, unitroot_nsdiffs)      # the output is just a blank row
#> # A tibble: 1 x 1
#>   nsdiffs
#>     <int>
#> 1       1

## If I filter out the NA in the first row from the first differencing…
AirPass %>% 
  mutate(Dpass = difference(log(pass), lag = 1)) %>%
  slice(2:nrow(AirPass)) %>% 
  features(Dpass, unitroot_nsdiffs)    # reports minimum seasonal differences = 1
#> # A tibble: 1 x 1
#>   nsdiffs
#>     <int>
#> 1       1

^{Created on 2019-07-22 by the reprex package (v0.3.0)}