式給出：R一欄，發現該列的副本中data.frame

Question

鑑於以下數據：

questionTagMatrix <- data.frame(question1=c("0","1","0"), question2=c("1","0", "0"), question3=c("0","1","0"), question4=c("0","1","1") ) 
rownames(questionTagMatrix)[1] <- "php" 
rownames(questionTagMatrix)[2] <- "html" 
rownames(questionTagMatrix)[3] <- "javascript" 

newQuestion <- data.frame(newquestion=c("0","1","0")) 
rownames(newQuestion)[1] <- "php" 
rownames(newQuestion)[2] <- "html" 
rownames(newQuestion)[3] <- "javascript" 

如何找到等於newQuestion的questionTagMatrix所有列？

Answer 1

您可以使用apply找到列：

questionTagMatrix[apply(questionTagMatrix, 2, function(x) 
               all(x == as.matrix(newQuestion)))] 

的questionTagMatrix所有列與newQuestion比較。其結果是：

#   question1 question3 
# php    0   0 
# html    1   1 
# javascript   0   0 

Answer 2

使用colSums矢量化的解決方案：

questionTagMatrix[,colSums(questionTagMatrix == newQuestion) 
        ==nrow(questionTagMatrix)] 

      question1 question3 
php    0   0 
html    1   1 
javascript   0   0 

PS newQuestion是一個向量在這裏：

newQuestion =c("0","1","0") ## not data.frame(newquestion=c("0","1","0")) 

要獲得唯一的問題名稱：

names(questionTagMatrix)[colSums(questionTagMatrix == newQuestion) 
+     ==nrow(questionTagMatrix)] 
[1] "question1" "question3"