Use group_indices() in mutate() with nse

[benmarwick]

Can we get group_indices to work in mutate using non-standard evaluation?

Often we want to add the output of group_indices back to the dataframe for further manipulation. It is possible with se, but it's a lot of typing and could be more novice-friendly.

This would be good if it would work:

mtcars %>%  mutate(group = group_indices(cyl))
Error: no applicable method for 'group_indices_' applied to an object of class "c('double', 'numeric')"

Instead we have to do this, using the se version:

  mtcars %>% mutate(group = group_indices_(., .dots="cyl"))

 mpg cyl  disp  hp drat    wt  qsec vs am gear carb group
1  21.0   6 160.0 110 3.90 2.620 16.46  0  1    4    4     2
2  21.0   6 160.0 110 3.90 2.875 17.02  0  1    4    4     2
3  22.8   4 108.0  93 3.85 2.320 18.61  1  1    4    1     1
4  21.4   6 258.0 110 3.08 3.215 19.44  1  0    3    1     2
5  18.7   8 360.0 175 3.15 3.440 17.02  0  0    3    2     3
6  18.1   6 225.0 105 2.76 3.460 20.22  1  0    3    1     2
7  14.3   8 360.0 245 3.21 3.570 15.84  0  0    3    4     3
8  24.4   4 146.7  62 3.69 3.190 20.00  1  0    4    2     1
9  22.8   4 140.8  95 3.92 3.150 22.90  1  0    4    2     1
10 19.2   6 167.6 123 3.92 3.440 18.30  1  0    4    4     2
11 17.8   6 167.6 123 3.92 3.440 18.90  1  0    4    4     2

[krlmlr]

With #2190, the following works for me:

mtcars %>%  mutate(., group = group_indices(., cyl))

@hadley: Should we simplify this any further?

[hadley]

That seems reasonable to me.

[krlmlr]

In particular: Should the following work:

mtcars %>%  mutate(group = group_indices(cyl))

[hadley]

I don't think so. We could develop a function that did work like that, but it would need to be a new function since it wouldn't be backward compatible.

[krlmlr]

Yeah, we already have row_number(x) vs. row_number() (#2218).

[sluedtke]

Hi,

I am still running into problems with that issue, Rstudio freezes (and restarts with a new session) and within vim (and vim-r-plugin) R crashes with *** Error in /usr/lib/R/bin/exec/R': free(): invalid pointer: 0x0000000009ff8ca8 *** `

library(dplyr)
temp = data.frame(a = rep(c(2, 3, 4), each=4), 
                  b = seq(1, 12))

# that fails as mentioned before
mutate(temp, id = group_indices(a))

# that fails, not expected 
temp %>% mutate(., id = group_indices(., a))

#that fails, not expected ;-) 
mtcars %>%  mutate(., group = group_indices(., cyl))

# that works
temp$id = group_indices(temp, a)

Session details:

> sessionInfo()
R version 3.3.2 (2016-10-31)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: KDE neon User Edition 5.8

locale:
 [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C               LC_TIME=en_GB.UTF-8       
 [4] LC_COLLATE=en_GB.UTF-8     LC_MONETARY=en_GB.UTF-8    LC_MESSAGES=en_GB.UTF-8   
 [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C                  LC_ADDRESS=C              
[10] LC_TELEPHONE=C             LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] dplyr_0.5.0    colorout_1.0-3

loaded via a namespace (and not attached):
[1] magrittr_1.5   R6_2.1.2       assertthat_0.1 DBI_0.4-1      tools_3.3.2    tibble_1.2    
[7] Rcpp_0.12.5   

Any help is appreciated.