Question

此函数应采用用户在第一个readline()提示符中输入的整数，然后根据该整数运行readline()输入的下一部分。

如果numSampFolders == 1，则根据下面的代码，它只需要一个示例文件夹名称。同样，如果numSampFolders == 2，那么它需要两个示例文件夹名称。

必须有一个更好的方式来写这个，而不是我如何设置它（并且我真的不想最终得到几十个if()语句只是为了涵盖每一个可能性...... ）。例如，如果numSampFolders = 24，则代码应通过readline()要求用户输入24个名称并将这些名称存储为全局变量。（我知道使用list.files()可以更轻松地完成此操作，但是同一目录中的文件夹不是必需的。）谢谢您的想法。

set_params <- function(){
    numSampFolders <- (readline("How many sample folders are you using? "))
    numSampFolders <<- as.numeric(numSampFolders)
    if (numSampFolders == 1)
        SampFolder1 <<- readline("Enter the name of your only sample folder: ")
    if (numSampFolders == 2)
        SampFolder1 <<- readline("Enter the name of sample folder 1: ")
        SampFolder2 <<- readline("Enter the name of sample folder 2: ")
}
if(interactive()) set_params()

Answer 1

一般方法是使用lapply（或sapply/for）进行迭代，使用R动词assign。 assign的行为与<-相似，让assign行为与<<-相似的技巧是指定envir = .GlobalEnv的环境。请参阅以下解决方案

set_params <- function(){
    numSampFolders <- (readline("How many sample folders are you using? "))
    numSampFolders <<- as.numeric(numSampFolders)
    if (numSampFolders == 1) {
        SampFolder1 <<- readline("Enter the name of your only sample folder: ")
    } else if (numSampFolders > 1) {
        lapply(seq_len(numSampFolders), function(i) assign(paste0("SampFolder", i), readline(paste0("Enter the name of sample folder ", i, ": ")), envir = .GlobalEnv))
    }
}
if(interactive()) set_params()

这是我的控制台的输出

ls()
# character(0)

# How many sample folders are you using? 2
# Enter the name of sample folder 1: ok
# Enter the name of sample folder 2: whatever
# [[1]]
# [1] "ok"

# [[2]]
# [1] "whatever"

ls()
# [1] "numSampFolders" "SampFolder1"    "SampFolder2"    "set_params"

SampFolder1  
# [1] "ok"

您可能不希望lapply将值打印到控制台（在这种情况下，这是副作用）。以下是我所指的

# [[1]]
# [1] "ok"

在这种情况下，您可以使用purrr::walk循环而不会产生副作用。

library(purrr)
set_params <- function(){
    numSampFolders <- (readline("How many sample folders are you using? "))
    numSampFolders <<- as.numeric(numSampFolders)
    if (numSampFolders == 1) {
        SampFolder1 <<- readline("Enter the name of your only sample folder: ")
    } else if (numSampFolders > 1) {
        walk(seq_len(numSampFolders), function(i) assign(paste0("SampFolder", i), readline(paste0("Enter the name of sample folder ", i, ": ")), envir = .GlobalEnv))
    }
}

if(interactive()) set_params()

重复和递增readline（）用户输入x次

1 个答案: