R: 神の作りし関数 dplyr::group_walk() を君は知っているか。

# 知らなかった人は今日感動するべき：

```R:grouped_tibble_to_tsv_files.R
# なんでもよいのでグループ化して
res %<>% group_by(storename)

#グループ別に.tsvファイルに書き出す
res %>% group_walk(~ write_csv(.x, paste0("res_", .y$storename, ".tsv")))
```
超短い手抜きエントリーですが、つどカスタム関数書いてた人多いのでは？
やばいぜあついぜ tidyverse、アツクテシヌゼ...
0.8.0以降からの新機能との事。

たまに公式を読み返そうと思いました：
https://dplyr.tidyverse.org/reference/group_map.html


さてあまりに記事が短いのでここで「dplyr言えるかな音頭〜♫」
さぁどれだけ言えるかな？

```
> pacman::p_funs(dplyr)
  [1] ".data"               "%>%"                 "add_count"           "add_count_"         
  [5] "add_row"             "add_rownames"        "add_tally"           "add_tally_"         
  [9] "all_equal"           "all_vars"            "anti_join"           "any_vars"           
 [13] "arrange"             "arrange_"            "arrange_all"         "arrange_at"         
 [17] "arrange_if"          "as_data_frame"       "as_tibble"           "as.tbl"             
 [21] "as.tbl_cube"         "auto_copy"           "bench_tbls"          "between"            
 [25] "bind_cols"           "bind_rows"           "case_when"           "changes"            
 [29] "check_dbplyr"        "coalesce"            "collapse"            "collect"            
 [33] "combine"             "common_by"           "compare_tbls"        "compare_tbls2"      
 [37] "compute"             "contains"            "copy_to"             "count"              
 [41] "count_"              "cumall"              "cumany"              "cume_dist"          
 [45] "cummean"             "current_vars"        "data_frame"          "data_frame_"        
 [49] "db_analyze"          "db_begin"            "db_commit"           "db_create_index"    
 [53] "db_create_indexes"   "db_create_table"     "db_data_type"        "db_desc"            
 [57] "db_drop_table"       "db_explain"          "db_has_table"        "db_insert_into"     
 [61] "db_list_tables"      "db_query_fields"     "db_query_rows"       "db_rollback"        
 [65] "db_save_query"       "db_write_table"      "dense_rank"          "desc"               
 [69] "dim_desc"            "distinct"            "distinct_"           "distinct_all"       
 [73] "distinct_at"         "distinct_if"         "distinct_prepare"    "do"                 
 [77] "do_"                 "dr_dplyr"            "ends_with"           "enexpr"             
 [81] "enexprs"             "enquo"               "enquos"              "ensym"              
 [85] "ensyms"              "eval_tbls"           "eval_tbls2"          "everything"         
 [89] "explain"             "expr"                "failwith"            "filter"             
 [93] "filter_"             "filter_all"          "filter_at"           "filter_if"          
 [97] "first"               "frame_data"          "full_join"           "funs"               
[101] "funs_"               "glimpse"             "group_by"            "group_by_"          
[105] "group_by_all"        "group_by_at"         "group_by_if"         "group_by_prepare"   
[109] "group_cols"          "group_data"          "group_indices"       "group_indices_"     
[113] "group_keys"          "group_map"           "group_nest"          "group_rows"         
[117] "group_size"          "group_split"         "group_trim"          "group_vars"         
[121] "group_walk"          "grouped_df"          "groups"              "hybrid_call"        
[125] "id"                  "ident"               "if_else"             "inner_join"         
[129] "intersect"           "is_grouped_df"       "is.grouped_df"       "is.src"             
[133] "is.tbl"              "lag"                 "last"                "last_col"           
[137] "lead"                "left_join"           "location"            "lst"                
[141] "lst_"                "make_tbl"            "matches"             "min_rank"           
[145] "mutate"              "mutate_"             "mutate_all"          "mutate_at"          
[149] "mutate_each"         "mutate_each_"        "mutate_if"           "n"                  
[153] "n_distinct"          "n_groups"            "na_if"               "near"               
[157] "nest_join"           "new_grouped_df"      "nth"                 "ntile"              
[161] "num_range"           "one_of"              "order_by"            "percent_rank"       
[165] "progress_estimated"  "pull"                "quo"                 "quo_name"           
[169] "quos"                "rbind_all"           "rbind_list"          "recode"             
[173] "recode_factor"       "rename"              "rename_"             "rename_all"         
[177] "rename_at"           "rename_if"           "rename_vars"         "rename_vars_"       
[181] "right_join"          "row_number"          "rowwise"             "same_src"           
[185] "sample_frac"         "sample_n"            "select"              "select_"            
[189] "select_all"          "select_at"           "select_if"           "select_var"         
[193] "select_vars"         "select_vars_"        "semi_join"           "setdiff"            
[197] "setequal"            "show_query"          "slice"               "slice_"             
[201] "sql"                 "sql_escape_ident"    "sql_escape_string"   "sql_join"           
[205] "sql_select"          "sql_semi_join"       "sql_set_op"          "sql_subquery"       
[209] "sql_translate_env"   "src"                 "src_df"              "src_local"          
[213] "src_mysql"           "src_postgres"        "src_sqlite"          "src_tbls"           
[217] "starts_with"         "summarise"           "summarise_"          "summarise_all"      
[221] "summarise_at"        "summarise_each"      "summarise_each_"     "summarise_if"       
[225] "summarize"           "summarize_"          "summarize_all"       "summarize_at"       
[229] "summarize_each"      "summarize_each_"     "summarize_if"        "sym"                
[233] "syms"                "tally"               "tally_"              "tbl"                
[237] "tbl_cube"            "tbl_df"              "tbl_nongroup_vars"   "tbl_sum"            
[241] "tbl_vars"            "tibble"              "top_n"               "transmute"          
[245] "transmute_"          "transmute_all"       "transmute_at"        "transmute_if"       
[249] "tribble"             "trunc_mat"           "type_sum"            "ungroup"            
[253] "union"               "union_all"           "validate_grouped_df" "vars"               
[257] "with_order"          "wrap_dbplyr_obj"    
```