在r中的正则表达式内粘贴带引号的变量

Question

我的问题的核心是使用“粘贴”将变量放入正则表达式中，并使用转义字符作为引号。这是其他 stackoverflow 问题的答案——但它似乎不起作用。我认为这个问题的独特之处在于它结合了这两个元素——使用粘贴将变量放入正则表达式，并使用转义字符作为引号。我也尝试过使用“cat”，这是另一个常见的答案，但没有成功。

我正在尝试做的是通过包含数千个名称的列表更轻松地按名称进行过滤。 （我正在从可视化软件 (Spotfire) 迁移到 R，但我错过了列表框过滤器。）我会很高兴收到有关如何执行此任务的任何建议。

而且，是的，我是 R 编程（以及一般编程）的新手。Stackoverflow 一直是最好的资源。你们一定是一群天才，

谢谢--

# mtcars example for filtering and finding names for the stack overflow question

data(mtcars)

# make the data match my dataframe, where I don't have row names but have a column with the name
mtcars$carname  <- NA  #declare the variable
mtcars$carname  <- rownames(mtcars) #assign the names to a column

findcar  <- function() {

  while(TRUE) {
    print("Type the car's name:")     
    apxname  <- readline() #approx name
    #type in Merc for this example
    carlst  <- mtcars$carname[(grepl("(apxname)",mtcars$carname, ignore.case = TRUE))] #list of cars that matches the approximate name
          # if I type   . . . (grepl("(Merc)", mtcars$carname, . . . )) it works great
    #So per other stackoverflow responses, I've tried using "paste" or "paste0" without success
    #I can't get this to work
    #carlst  <- mtcars$carname[(grepl(paste0('\"(',apxname, ')\"', sep=""),mtcars$carname, ignore.case = TRUE))]
    print("Here's the list of similar customers:")
    print(carlst)
    print("Type the number of your car:")
    carnum  <- readline()  #car number
    therightone  <- carlst[as.numeric(carnum)] 
    paste("You selected",therightone,"Is this the car (Y/N)?", sep=" ")
    carconf  <- readline()  #car confirmation
    if(carconf == "Y") break)
  }
return(therightone)
}

Answer 1

要解决特定问题，请将 apxname 引用为变量，而不是字符串。稍微清理了一下，包括上面 Mathias 提到的错别字以及将汽车确认提示包裹在print：

findcar  <- function() {

    while(TRUE) {
        print("Type the car's name:")     
        apxname  <- readline() # approx name
        # list of cars that matches the approximate name
        carlst  <- rownames(mtcars)[grepl(apxname, rownames(mtcars), ignore.case = TRUE)]
        print("Here's the list of similar customers:")
        print(carlst)
        print("Type the number of your car:")
        carnum  <- readline()  # car number
        therightone  <- carlst[as.numeric(carnum)] 
        print(paste("You selected",therightone,"Is this the car (Y/N)?", sep=" "))
        carconf  <- readline()  # car confirmation
        if(carconf == "Y") break
    }
    return(therightone)
}

此版本返回汽车名称；如果你想返回汽车的所有统计数据，你需要类似的东西

findcar  <- function() {

    while(TRUE) {
        print("Type the car's name:")     
        apxname  <- readline() # approx name
        # list of cars that matches the approximate name
        carlst  <- mtcars[grepl(apxname, rownames(mtcars), ignore.case = TRUE),]
        print("Here's the list of similar customers:")
        print(carlst)
        print("Type the number of your car:")
        carnum  <- readline()  # car number
        therightone  <- carlst[as.numeric(carnum),] 
        print(paste("You selected",rownames(therightone),"Is this the car (Y/N)?", sep=" "))
        carconf  <- readline()  # car confirmation
        if(carconf == "Y") break
    }
    return(therightone)
}

“选择一个数字”提示可以使用工作，因为没有打印行号，但至少可以工作。