R - 提取匹配和不匹配字符串的部分

Question

我需要提取两列之间匹配和不匹配的字符串部分：

x <- c("apple, banana, pine nuts, almond")
y <- c("orange, apple, almond, grapes, carrots")
j <- data.frame(x,y)

获得：

yonly <- c("orange, grapes, carrots")
xonly <- c("banana, pine nuts")
both <- c("apple, almond")
k <- data.frame(cbind(x,y,both,yonly,xonly))

我研究了 str_detect、相交等，但这些似乎需要对现有细胞进行大手术才能将它们分成不同的细胞。这是一个包含其他列的相当大的数据集，所以我不想对它进行太多操作。你能帮我想出一个更简单的解决方案吗？

谢谢！

Answer 1

您可以使用 setdiff 和 intersect

> j <- data.frame(x,y, stringsAsFactors = FALSE)
> X <- strsplit(j$x, ",\s*")[[1]]
> Y <- strsplit(j$y, ",\s*")[[1]]
> 
> #Yonly
> setdiff(Y, X)
[1] "orange"  "grapes"  "carrots"
> 
> #Xonly
> setdiff(X, Y)
[1] "banana"    "pine nuts"
> 
> #Both
> intersect(X, Y)
[1] "apple"  "almond"

Answer 2

要按照您的描述创建更长数据帧的额外列 j，您可以使用 mapply 和 Jilber Urbina 的回答中使用的方法...

#set up data
x <- c("apple, banana, pine nuts, almond")
y <- c("orange, apple, almond, grapes, carrots")
j <- data.frame(x,y,stringsAsFactors = FALSE)

j[,c("yonly","xonly","both")] <- mapply(function(x,y) {
                    x2 <- unlist(strsplit(x, ",\s*"))
                    y2 <- unlist(strsplit(y, ",\s*"))
                    yonly <- paste(setdiff(y2, x2), collapse=", ")
                    xonly <- paste(setdiff(x2, y2), collapse=", ")
                    both <- paste(intersect(x2, y2), collapse=", ")
                    return(c(yonly, xonly, both))      },
                                        j$x,j$y)

j
                                 x                                      y                   yonly             xonly          both
1 apple, banana, pine nuts, almond orange, apple, almond, grapes, carrots orange, grapes, carrots banana, pine nuts apple, almond

R - 提取匹配和不匹配字符串的部分

R - Extract portions of matching and non matching strings

string

r

string-comparison

dataframe