count() does not work, n() does

[szarnyasg]

I found that the following script fails:

library("duckplyr")

iris |>
    group_by(Species) |>
    summarize(num_observations = count()) |>
    collect()

The duckplyr package is configured to fall back to dplyr when it encounters an incompatibility. Fallback events can be collected and
uploaded for analysis to guide future development. By default, data will be collected but no data will be uploaded.
ℹ Automatic fallback uploading is not controlled and therefore disabled, see `?duckplyr::fallback()`.
✔ Number of reports ready for upload: 5.
→ Review with `duckplyr::fallback_review()`, upload with `duckplyr::fallback_upload()`.
ℹ Configure automatic uploading with `duckplyr::fallback_config()`.
✔ Overwriting dplyr methods with duckplyr methods.
ℹ Turn off with `duckplyr::methods_restore()`.
Error in `summarize()`:
ℹ In argument: `num_observations = count()`.
ℹ In group 1: `Species = setosa`.
Caused by error in `UseMethod()`:
! no applicable method for 'count' applied to an object of class "NULL"
Run `rlang::last_trace()` to see where the error occurred.

Replacing count() to n() makes it work:

library("duckplyr")

iris |>
    group_by(Species) |>
    summarize(num_observations = n()) |>
    collect()

# A tibble: 3 × 2
  Species    num_observations
  <fct>                 <int>
1 setosa                   50
2 versicolor               50
3 virginica                50

[krlmlr]

Thanks. I also see:

options(conflicts.policy = list(warn = FALSE))
library(dplyr)

iris |>
  group_by(Species) |>
  summarize(num_observations = count()) |>
  collect()
#> Error in `summarize()`:
#> ℹ In argument: `num_observations = count()`.
#> ℹ In group 1: `Species = setosa`.
#> Caused by error in `UseMethod()`:
#> ! no applicable method for 'count' applied to an object of class "NULL"

^{Created on 2025-02-14 with reprex v2.1.1}

count() is a verb to be used instead of summarize() . But we don't support factors yet:

options(conflicts.policy = list(warn = FALSE))
library(dplyr)

iris |>
  duckplyr::as_duckdb_tibble(prudence = "stingy") |>
  count(Species) |>
  collect()
#> Error in `duckdb_rel_from_df()` at duckplyr/R/duckplyr_df.R:20:5:
#> ! Can't convert columns of class <factor> to relational. Affected
#>   column: `Species`.

^{Created on 2025-02-14 with reprex v2.1.1}

(Need a better error message here too.)

This will work and use DuckDB:

options(conflicts.policy = list(warn = FALSE))
library(dplyr)

iris |>
  mutate(Species = as.character(Species)) |>
  duckplyr::as_duckdb_tibble(prudence = "stingy") |>
  count(Species) |>
  collect()
#> # A tibble: 3 × 2
#>   Species        n
#>   <chr>      <int>
#> 1 setosa        50
#> 2 versicolor    50
#> 3 virginica     50

^{Created on 2025-02-14 with reprex v2.1.1}

[krlmlr]

Better error message with #614.

[szarnyasg]

Great, thanks!