Error in unique.default(x, nmax = nmax): unique() applies only to vectors

[XiangyunHuang]

do.call("rbind.data.frame", lapply(base::split(x = iris, ~Species), head))
#>               Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
#> setosa.1               5.1         3.5          1.4         0.2     setosa
#> setosa.2               4.9         3.0          1.4         0.2     setosa
#> setosa.3               4.7         3.2          1.3         0.2     setosa
#> setosa.4               4.6         3.1          1.5         0.2     setosa
#> setosa.5               5.0         3.6          1.4         0.2     setosa
#> setosa.6               5.4         3.9          1.7         0.4     setosa
#> versicolor.51          7.0         3.2          4.7         1.4 versicolor
#> versicolor.52          6.4         3.2          4.5         1.5 versicolor
#> versicolor.53          6.9         3.1          4.9         1.5 versicolor
#> versicolor.54          5.5         2.3          4.0         1.3 versicolor
#> versicolor.55          6.5         2.8          4.6         1.5 versicolor
#> versicolor.56          5.7         2.8          4.5         1.3 versicolor
#> virginica.101          6.3         3.3          6.0         2.5  virginica
#> virginica.102          5.8         2.7          5.1         1.9  virginica
#> virginica.103          7.1         3.0          5.9         2.1  virginica
#> virginica.104          6.3         2.9          5.6         1.8  virginica
#> virginica.105          6.5         3.0          5.8         2.2  virginica
#> virginica.106          7.6         3.0          6.6         2.1  virginica

library(data.table)

iris <- as.data.table(iris)

do.call("rbind.data.frame", lapply(base::split(x = iris, ~Species), head))
#> Error in unique.default(x, nmax = nmax): unique() applies only to vectors

sessionInfo()
#> R version 4.2.0 (2022-04-22)
#> Platform: x86_64-apple-darwin17.0 (64-bit)
#> Running under: macOS Big Sur/Monterey 10.16
#> 
#> Matrix products: default
#> BLAS:   /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRblas.0.dylib
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.2/Resources/lib/libRlapack.dylib
#> 
#> locale:
#> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] data.table_1.14.2
#> 
#> loaded via a namespace (and not attached):
#>  [1] rstudioapi_0.13   knitr_1.39        magrittr_2.0.3    R.cache_0.15.0   
#>  [5] rlang_1.0.2       fastmap_1.1.0     fansi_1.0.3       stringr_1.4.0    
#>  [9] styler_1.7.0      highr_0.9         tools_4.2.0       xfun_0.31        
#> [13] R.oo_1.24.0       utf8_1.2.2        cli_3.3.0         withr_2.5.0      
#> [17] htmltools_0.5.2   ellipsis_0.3.2    yaml_2.3.5        digest_0.6.29    
#> [21] tibble_3.1.7      lifecycle_1.0.1   crayon_1.5.1      purrr_0.3.4      
#> [25] R.utils_2.11.0    vctrs_0.4.1       fs_1.5.2          glue_1.6.2       
#> [29] evaluate_0.15     rmarkdown_2.14    reprex_2.0.1      stringi_1.7.6    
#> [33] compiler_4.2.0    pillar_1.7.0      R.methodsS3_1.8.1 pkgconfig_2.0.3

^{Created on 2022-05-24 by the reprex package (v2.0.1)}

[MichaelChirico]

IIUC this is a request for is.formula(f) to work with data.table's split method

[XiangyunHuang]

Yeah! Is it possible to support formula syntax in data.table?

[ben-schwen]

@XiangyunHuang totally possible but not sure if wanted. Will work on a PR. (1-liner if we take over the eval from split.data.frame).

[MichaelChirico]

at the very least we should fail more gracefully. but I don't see any problem with supporting this either for parity with data.frame.

[MichaelChirico]

No wonder I had never heard of this before -- it's a very new base R feature!

r-devel/r-svn@82b4382

[YuyanCao]

Hi, did you work it out? I also met this problem when using R

[jangorecki]

Try out linked PR and tell us if it works for you.