as_tibble（）无法正常工作

Question

I am attempting the exercise in R for data science (7.5.2.1, #2): Use geom_tile() together with dplyr to explore how average flight delays vary by destination and month of year. What makes the plot difficult to read? How could you improve it?

First, transmute columns.

library(nycflights13)
foo <- nycflights13::flights %>%
  transmute(tot_delay = dep_delay + arr_delay, m = month, d = dest) %>%
  filter(!is.na(tot_delay)) %>%
  group_by(m, d) %>%
  summarise(avg_delay = mean(tot_delay))

Now foo appears to be a data frame based on the 'Source' output.

> foo
Source: local data frame [1,112 x 3]
Groups: m [?]

       m     d avg_delay
   <int> <chr>     <dbl>
1      1   ALB 76.571429
2      1   ATL  8.567982
3      1   AUS 19.017751
4      1   AVL 49.000000
5      1   BDL 32.081081
6      1   BHM 47.043478
7      1   BNA 25.930233
8      1   BOS  2.698517
9      1   BQN  8.516129
10     1   BTV 18.393665
# ... with 1,102 more rows

It doesn't appear that as_tibble is working, what could I be doing wrong?

> as_tibble(foo)
Source: local data frame [1,112 x 3]
Groups: m [?]

       m     d avg_delay
   <int> <chr>     <dbl>
1      1   ALB 76.571429
2      1   ATL  8.567982
3      1   AUS 19.017751
4      1   AVL 49.000000
5      1   BDL 32.081081
6      1   BHM 47.043478
7      1   BNA 25.930233
8      1   BOS  2.698517
9      1   BQN  8.516129
10     1   BTV 18.393665
# ... with 1,102 more rows

Shouldn't the internals be different for a tibble?

> str(foo)
Classes ‘grouped_df’, ‘tbl_df’, ‘tbl’ and 'data.frame': 1112 obs. of  3 variables:
 $ m        : int  1 1 1 1 1 1 1 1 1 1 ...
 $ d        : chr  "ALB" "ATL" "AUS" "AVL" ...
 $ avg_delay: num  76.57 8.57 19.02 49 32.08 ...
 - attr(*, "vars")=List of 1
  ..$ : symbol m
 - attr(*, "drop")= logi TRUE
> str(as_tibble(foo))
Classes ‘grouped_df’, ‘tbl_df’, ‘tbl’ and 'data.frame': 1112 obs. of  3 variables:
 $ m        : int  1 1 1 1 1 1 1 1 1 1 ...
 $ d        : chr  "ALB" "ATL" "AUS" "AVL" ...
 $ avg_delay: num  76.57 8.57 19.02 49 32.08 ...
 - attr(*, "vars")=List of 1
  ..$ : symbol m
 - attr(*, "drop")= logi TRUE

Note that as_tibble() works as expected

> packageDescription("tibble")
Package: tibble
Encoding: UTF-8
Version: 1.3.0

> is_tibble(foo)
[1] TRUE

Answer 1

Works for me - foo is a "tibble" and is announced as "A tibble: 112 x 3" in the print:

> foo
Source: local data frame [1,112 x 3]
Groups: m [?]

# A tibble: 1,112 x 3
       m     d avg_delay
   <int> <chr>     <dbl>
 1     1   ALB 76.571429
 2     1   ATL  8.567982

So you possibly have an old version of dplyr. Mine is:

> packageDescription("dplyr")
Package: dplyr
Type: Package
Version: 0.5.0

And everything else:

> sessionInfo()
R version 3.3.1 (2016-06-21)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 14.04.4 LTS

locale:
 [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_GB.UTF-8        LC_COLLATE=en_GB.UTF-8    
 [5] LC_MONETARY=en_GB.UTF-8    LC_MESSAGES=en_GB.UTF-8   
 [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] 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  tibble_1.3.1

loaded via a namespace (and not attached):
[1] magrittr_1.5     R6_2.2.0         assertthat_0.2.0 DBI_0.5-1       
[5] tools_3.3.1      Rcpp_0.12.11     rlang_0.1.1