Possible bug with integer dates input

[thibautjombart]

Please place an "x" in all the boxes that apply

• I have the most recent version of incidence2 and R
• I have found a bug
• I have a reproducible example
• I want to request a new feature

---

I think the following should probably work; I am guessing it has to do with dates being simple numbers (not Date or grates stuff) but not 100% sure. Here's a reprex:

library(incidence2)

df <- data.frame(
  dates = 1:100,
  counts = round(rnorm(100, 1000, 200))
)

x <- incidence(df, date_index = dates, counts = counts)
x
#> An incidence2 object: 100 x 2
#> 100028 counts from 1 to 100
#> interval: 1 day
#> cumulative: FALSE
#> 
#>    date_index counts
#>         <int>  <dbl>
#>  1          1    775
#>  2          2   1389
#>  3          3   1341
#>  4          4    999
#>  5          5    694
#>  6          6    645
#>  7          7   1000
#>  8          8   1365
#>  9          9   1119
#> 10         10    959
#> # … with 90 more rows
plot(x)
#> Error in `substring<-`(`*tmp*`, 1, 1, value = toupper(first_letter)): replacing substrings in a non-character object

^{Created on 2021-03-29 by the reprex package (v1.0.0)}