给定一个列，在data.frame中查找该列的重复项

Question

鉴于以下数据：

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questionTagMatrix的所有列都等于newQuestion

Answer 1

您可以使用apply查找以下列：

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

将questionTagMatrix的所有列与newQuestion进行了比较。结果：

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

Answer 2

基于colSums的矢量化解决方案

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

          question1 question3
php                0         0
html               1         1
javascript         0         0

PS newQuestion是这里的一个向量：

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

要只得到问题的名字：

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