filtering a grouped table removes indices attribute

[Mullefa]

For example:

# OK
iris %>% 
  group_by(Species) %>%
  attr("indices")

# not OK
iris %>% 
  group_by(Species) %>%
  filter(n() > 0) %>%
  attr("indices")

devtools::session_info()
# dplyr        0.4.0.9000 2015-01-11 Github (hadley/dplyr@cd91f33)    

If this is intended (I imagine its not), then at least the n_groups() method for a grouped_df needs to be fixed.

[romainfrancois]

Seems to no longer be the case:

# not OK
> iris %>%
+   group_by(Species) %>%
+   filter(n() > 0) %>%
+   attr("indices")
[[1]]
 [1]  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
[26] 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

[[2]]
 [1] 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
[26] 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

[[3]]
 [1] 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
[20] 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137
[39] 138 139 140 141 142 143 144 145 146 147 148 149

However, there seems to be a problem, indices are not updated at all :

> res <- iris %>% group_by(Species) %>% filter( Sepal.Length > 5 )
> res
Source: local data frame [118 x 5]
Groups: Species

   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1           5.1         3.5          1.4         0.2  setosa
2           5.4         3.9          1.7         0.4  setosa
3           5.4         3.7          1.5         0.2  setosa
4           5.8         4.0          1.2         0.2  setosa
5           5.7         4.4          1.5         0.4  setosa
6           5.4         3.9          1.3         0.4  setosa
7           5.1         3.5          1.4         0.3  setosa
8           5.7         3.8          1.7         0.3  setosa
9           5.1         3.8          1.5         0.3  setosa
10          5.4         3.4          1.7         0.2  setosa
..          ...         ...          ...         ...     ...
> res %>% attr("indices")
[[1]]
 [1]  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
[26] 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

[[2]]
 [1] 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74
[26] 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99

[[3]]
 [1] 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
[20] 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137
[39] 138 139 140 141 142 143 144 145 146 147 148 149