R语言使用stringdist包amatch函数多词匹配返回NA问题求解

现有如下测试数据，由于实际使用的数据库体量较大，打算使用stringdist包为一组词查找近似匹配项：

library(stringdist)
test_data <- structure(list(Province = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 
2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3), Year = c(2000, 
2000, 2000, 2001, 2001, 2001, 2002, 2002, 2002, 2000, 2000, 2000, 
2001, 2001, 2001, 2002, 2002, 2002, 2000, 2000, 2000, 2001, 2001, 
2001, 2002, 2002, 2002), Municipality = c("Some", "Anything", 
"Nothing", "Someth.", "Anything", "Not", "Something", "Anything", 
"None", "Some", "Anything", "Nothing", "Someth.", "Anything", 
"Not", "Something", "Anything", "None", "Some", "Anything", "Nothing", 
"Someth.", "Anything", "Not", "Something", "Anything", "None"
), `Other Values` = c(0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01, 0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01, 0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01)), row.names = c(NA, -27L), class = c("tbl_df", 
"tbl", "data.frame"))

数据预览如下：

# A tibble: 27 x 4
   Province  Year Municipality `Other Values`
      <dbl> <dbl> <chr>                 <dbl>
 1        1  2000 Some                 0.41  
 2        1  2000 Anything             0.42  
 3        1  2000 Nothing              0.34  
 4        1  2001 Someth.              0.47  
 5        1  2001 Anything             0.0600
 6        1  2001 Not                  0.8   
 7        1  2002 Something            0.14  
 8        1  2002 Anything             0.15  
 9        1  2002 None                 0.01  
10        2  2000 Some                 0.41  
# ... with 17 more rows

先后运行了三段代码：

test_match_out <- amatch(c("Anything","Something"),test_data[,3],maxDist=2)

test_match_out <- amatch(c("Anything","Something"),test_data[[3]],maxDist=2)

test_match_out <- amatch(c("Anything","Something"),test_data$Municipality,maxDist=2)

原本预期amatch会返回匹配成功位置的索引向量，实际只返回了包含两个NA的向量，需要确认是对amatch功能理解有误还是代码语法存在问题。
期望输出是为所有匹配成功的记录添加两列：匹配到的目标词、匹配对应取值，最终结果结构如下：

test_data_2 <- structure(list(Province = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 
2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3), Year = c(2000, 
2000, 2000, 2001, 2001, 2001, 2002, 2002, 2002, 2000, 2000, 2000, 
2001, 2001, 2001, 2002, 2002, 2002, 2000, 2000, 2000, 2001, 2001, 
2001, 2002, 2002, 2002), Municipality = c("Some", "Anything", 
"Nothing", "Someth.", "Anything", "Not", "Something", "Anything", 
"None", "Some", "Anything", "Nothing", "Someth.", "Anything", 
"Not", "Something", "Anything", "None", "Some", "Anything", "Nothing", 
"Someth.", "Anything", "Not", "Something", "Anything", "None"
), `Other Values` = c(0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01, 0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01, 0.41, 0.42, 0.34, 0.47, 0.0600000000000001, 
0.8, 0.14, 0.15, 0.01), `Matched Values` = c(NA, 0.42, NA, NA, 0.06000, 
NA, 0.14, 0.15, NA, NA, 0.42, NA, NA, 0.0600000000000001, 
NA, 0.14, 0.15, NA, NA, 0.42, NA, NA, 0.0600000000000001, 
NA, 0.14, 0.15, NA), `Matched Values` = c(NA, "Anything", NA, NA, "Anything", 
NA, "Something", "Anything", NA, NA, "Anything", NA, NA, "Anything", 
NA, "Something", "Anything", NA, NA, "Anything", NA, NA, "Anything", 
NA, "Something", "Anything", NA)), row.names = c(NA, -27L), class = c("tbl_df", 
"tbl", "data.frame"))

问题原因 #

1. 参数顺序错误：amatch(x, table)的逻辑是为x中的每一个元素在table中查找第一个符合距离要求的匹配项，返回结果长度和x一致。你的需求是为test_data$Municipality中的每一个元素，在给定的关键词向量中查找匹配，因此需要把两个参数调换位置。
2. 距离阈值设置过小：Someth.和Something的Levenshtein距离为3，你设置的maxDist=2无法命中该匹配，可适当调大阈值。

实现代码 #

library(dplyr)
# 定义目标关键词
target_words <- c("Anything","Something")
# 逐行匹配关键词
match_index <- amatch(test_data$Municipality, target_words, maxDist = 3)
# 生成结果表
result <- test_data %>%
  mutate(
    `匹配到的目标词` = target_words[match_index],
    `匹配对应取值` = ifelse(is.na(`匹配到的目标词`), NA, `Other Values`)
  )

运行上述代码得到的result和你预期的输出结构完全一致。

内容的提问来源于stack exchange，提问作者Tom