データが溶けずにRカウントが発生する

Question

wideデータセットの値に数えてを加算すると、のデータセットをlong（Person-Period）ファイルに変換する必要がありません。

私のデータは次のようになります。私は何をしたいか

 alone1 alone2  alone3  alone4  alone5  alone6  alone7  alone8 
1 Mentioned Mentioned  Mentioned  Mentioned  Mentioned  Mentioned  Mentioned  Mentioned 
2 Mentioned Mentioned  Mentioned  Mentioned  Mentioned  Mentioned  Mentioned  Mentioned 
3 Mentioned Mentioned Not mentioned Not mentioned Not mentioned Not mentioned Not mentioned Not mentioned 
4 Mentioned Mentioned Not mentioned Not mentioned Not mentioned Not mentioned Not mentioned Not mentioned 

が私を与えるこの

library(dplyr) 
library(tidyr) 

dt %>% gather %>% group_by(value) %>% summarise(n = n()) 

である（これは私が欲しい出力です）

  value n 
1  Mentioned 20 
2 Not mentioned 12 

しかし、私はしたくないですmeltまたはgather私データ。

人周期変換を行わずに列の出現をどのように数えることができますか？

dt = structure(list(alone1 = c("Mentioned", "Mentioned", "Mentioned", 
"Mentioned"), alone2 = c("Mentioned", "Mentioned", "Mentioned", 
"Mentioned"), alone3 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned"), alone4 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned"), alone5 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned"), alone6 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned"), alone7 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned"), alone8 = c("Mentioned", "Mentioned", "Not mentioned", 
"Not mentioned")), .Names = c("alone1", "alone2", "alone3", "alone4", 
"alone5", "alone6", "alone7", "alone8"), class = "data.frame", row.names = c(NA, 4L)) 

Answer 1

それはあなたが本当にちょうどあなたが使用することができますカウントtableとunlistあなたdata.frame

table(unlist(dt)) 

Mentioned Not mentioned 
     20   12