[英]Finding Matches Across Char Vectors in R
鉴于以下两个向量,有没有办法生成所需的数据帧? 这代表了一个现实世界的情况,我必须数据帧第一个包含一个带有数据库值(键)的列,第二个包含一个包含 1000+ 行的列,每个文件名(可能)我需要匹配。 问题是可以有多个文件(可能)与任何给定的键匹配。 我曾使用过 grep、合并、内部连接等,但无法将它们合并到一个解决方案中。 任何建议表示赞赏!
potentials <- c("tigerINTHENIGHT",
"tigerWALKINGALONE",
"bearOHMY",
"bearWITHME",
"rat",
"imatchnothing")
keys <- c("tiger",
"bear",
"rat")
desired <- data.frame(keys, c("tigerINTHENIGHT, tigerWALKINGALONE", "bearOHMY, bearWITHME", "rat"))
names(desired) <- c("key", "matches")
我认为的解决方案的伪代码:
#new column which is comma separated potentials
# x being the substring length i.e. x = 4 means true if first 4 letters match
function createNewColumn(keys, potentials, x){
str result = na
foreach(key in keys){
if(substring(key, 0, x) == any(substring(potentals, 0 ,x))){ //search entire potential vector
result += potential that matched + ', '
}
}
return new column with result as the value on the current row
}
我们可以编写一个小函数来提取匹配项,然后遍历键:
return_matches <- function(keys, potentials, fixed = TRUE) {
vapply(keys, function(k) {
paste(grep(k, potentials, value = TRUE, fixed = fixed), collapse = ", ")
}, FUN.VALUE = character(1))
}
vapply
只是sapply
的类型安全版本,这意味着它只会返回字符向量。 当您设置fixed = TRUE
时,function 将运行得更快,但不再识别正则表达式。 然后我们可以轻松制作所需的data.frame
:
df <- data.frame(
key = keys,
matches = return_matches(keys, potentials),
stringsAsFactors = FALSE
)
df
#> key matches
#> tiger tiger tigerINTHENIGHT, tigerWALKINGALONE
#> bear bear bearOHMY, bearWITHME
#> rat rat rat
将循环放在 function 中而不是直接运行它的原因只是为了使代码看起来更干净。
您可以使用grep
进行交互
> Match <- sapply(keys, function(item) {
paste0(grep(item, potentials, value = TRUE), collapse = ", ")
} )
> data.frame(keys, Match, row.names = NULL)
keys Match
1 tiger tigerINTHENIGHT, tigerWALKINGALONE
2 bear bearOHMY, bearWITHME
3 rat rat
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