R 在 warning() 中使用 cat() 将消息放在警告之前

Question

我使用 cat() 创建警告消息，但结果警告消息出现在“警告消息：”部分之前。是否有不同的方法来创建此警告消息，以便在“警告消息：”之后打印？

这就是输出的样子：

> acceptable_classes <- c(
+   "character", 
+   "gg", 
+   "ggplot", 
+   "data.frame", 
+   "flextable"
+ )
> 
> # This prints the correct way:
> if(TRUE){
+   warning("Some result is not an acceptable class.")
+ }
Warning message:
Some result is not an acceptable class. 
> 
> # This prints backwards:
> if(TRUE){
+   warning(
+     cat(
+       "Some result is not an acceptable class.",
+       "Acceptable classes are:", 
+       acceptable_classes, 
+       sep = "\n"
+     )
+   )
+ }
Some result is not an acceptable class.
Acceptable classes are:
character
gg
ggplot
data.frame
flextable
Warning message:

Answer 1

正如评论中提到的，您应该避免使用

cat

，而是使用

paste

，例如：

acceptable_classes <- letters[1:5]

if(TRUE){
  warning(
    paste(
      "Some result is not an acceptable class.",
      "Acceptable classes are:", 
      paste(acceptable_classes, collapse = ", "), 
      sep = "\n"
    )
  )
}

结果是：

Warning message:
Some result is not an acceptable class.
Acceptable classes are:
a, b, c, d, e