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mutate() loses groups #17

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hadley opened this issue Mar 8, 2016 · 1 comment

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@hadley
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@hadley hadley commented Mar 8, 2016

Moved from tidyverse/dplyr#919, by kykuo

library(dplyr)
library(dtplyr)

iris %>%
  group_by(Species) %>% 
  mutate(x = cumsum(Sepal.Length)) %>% 
  groups

data.table::data.table(iris) %>% 
  group_by(Species) %>%
  mutate(x = cumsum(Sepal.Length)) %>%
  groups
@HuangNa2

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@HuangNa2 HuangNa2 commented May 3, 2017

Seems like mutate reduces the group by 1 everytime its called

library(dplyr)
library(dtplyr)

iris %>%
  group_by(Species,Petal.Width,Sepal.Length) %>% 
  mutate(x = cumsum(Sepal.Length)) %>% 
  groups

Results in :

[[1]]
Species

[[2]]
Petal.Width

From a bit of testing it appears that it removes the last grouped element each time mutate is called.

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