在 function 中使用向量參數的名稱

Question

我正在編寫一個 function，它傳入一個值向量，我想在 function 中使用這些值進行計算。但是，我還想使用我傳遞的向量的名稱來返回有意義的錯誤消息，但無法確定知道怎么做。

我的 function 看起來像這樣

func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(paste0("The length of vector is less than ",minimumvalue))}
    else if (length(vector)>minimumvalue){
      stop(paste0("The length of vector is more than ",minimumvalue))}
    else (return(vector))
}

我的 function 電話是這樣的

colours <- c("red","green","blue")
func(colours, 2)

回報

“向量的長度大於2”，但我想說“顏色的長度大於2”

我可以通過添加另一個參數將矢量名稱作為字符串傳遞到 function 中來實現這一點，但我想知道是否有更好的設計方法。

Answer 1

我添加了deparse(substitute(vector))以將 object 的名稱作為字符串獲取。

func <- function(vector, minimumvalue){
  if(length(vector)==1){
    return(1)}
  else if (length(vector)<minimumvalue){
    stop(paste0("The length of ",deparse(substitute(vector))," is less than ",minimumvalue))}
  else if (length(vector)>minimumvalue){
    stop(paste0("The length of ",deparse(substitute(vector))," is more than ",minimumvalue))}
  else (return(vector))
}

colours <- c("red","green","blue")

func(colours, 2)

func(colours, 2) 錯誤：顏色的長度超過 2

Answer 2

使用glue水庫，您可以更輕松地格式化字符串：

library(glue)
func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(paste0(glue("The length of vector is less than "),minimumvalue))}
    else if (length(vector)>minimumvalue){
      stop(paste0(glue("The length of {substitute(vector)} is more than "),minimumvalue))}
    else (return(vector))
}

colours <- c("red","green","blue")
func(colours, 2)

Output：

Error in func(colours, 2) : 
The length of colours is more than 2

或者甚至更好地使用glue模塊來格式化minimumvalue ：

library(glue)
func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(glue("The length of {substitute(vector)} is less than {minimumvalue}"))}
    else if (length(vector)>minimumvalue){
      stop(glue("The length of {substitute(vector)} is more than {minimumvalue}"))}
    else (return(vector))
}

colours <- c("red","green","blue")
func(colours, 2)

你甚至不需要paste0 。