如何在我的字符向量和 output 另一個向量上應用這個 for 循環？

Question

我的代碼的目的是連接向量 v 中的值。為此，我創建了一個帶有兩個 arguments 向量 SID 的 function 連接。 但由於我不明白的原因，

#A character vector to which other strings will be appended
    
v <- c("R_2wmKOSbPWHl4VtT2","R_2TtslLEVNeHs2r73","R_ZF79IJ60LaxxsuR4","R_3JJDUkrZ07eIwnh5","R_3JrWuv9fsLK6qNx6")

concat <- function(vector,SID){
  
  decrement_append <- "&decrementQuotas=true"
  SID_append <- "?surveyId="
  
  for(i in 1:length(vector)){
    out[i] <- paste0(v[i],SID_append,SID,decrement_append)
  }
  out[i]
}

和：

concat(vector = v,
       SID = "SV_55tYjKDRKYTRNIh")

當我運行它時，我得到：

Error in concat(vector = v, SID = "SV_55tYjKDRKYTRNIh") : 
  object 'out' not found

我已經嘗試了其他幾種方法，例如：

   concat <- function(vector,SID){
  
  decrement_append <- "&decrementQuotas=true"
  SID_append <- "?surveyId="
  
  new_vector <- for(i in 1:length(vector)){
   out[i] <- paste0(v[i],SID_append,SID,decrement_append)
  }
  new_vector
}

但我遇到了同樣的錯誤。

Answer 1

在 function 中未初始化out

concat <- function(vector,SID){
   out <- character(length(vector))
  
   decrement_append <- "&decrementQuotas=true"
   SID_append <- "?surveyId="
  
   for(i in 1:length(vector)){
     out[i] <- paste0(v[i],SID_append,SID,decrement_append)
   }
   out
 }

-測試

> concat(v, "SV_55tYjKDRKYTRNIh")
[1] "R_2wmKOSbPWHl4VtT2?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true" "R_2TtslLEVNeHs2r73?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"
[3] "R_ZF79IJ60LaxxsuR4?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true" "R_3JJDUkrZ07eIwnh5?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"
[5] "R_3JrWuv9fsLK6qNx6?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"

---

paste/paste0是矢量化的。 所以，循環並不是真正需要的

concat2 <- function(vector,SID){
    
  
    decrement_append <- "&decrementQuotas=true"
    SID_append <- "?surveyId="
  
    
       paste0(v, SID_append,SID,decrement_append)
    

  }

-測試

> concat2(v, "SV_55tYjKDRKYTRNIh")
[1] "R_2wmKOSbPWHl4VtT2?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true" "R_2TtslLEVNeHs2r73?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"
[3] "R_ZF79IJ60LaxxsuR4?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true" "R_3JJDUkrZ07eIwnh5?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"
[5] "R_3JrWuv9fsLK6qNx6?surveyId=SV_55tYjKDRKYTRNIh&decrementQuotas=true"