Question

在开发R包时，我想使用R的{{1}}或message()函数为我的包用户生成输出。

有时这些消息可能很长。我可以这样做（文字只是一个简单的例子）：

warning()

很棒...但是对于样式，我也希望我的代码行少于80个字符，所以它们很适合在狭窄的屏幕上，在GitHub上等等。然后我可以使用一个IDE代码重排工具，可以在消息发生变化时轻松重新格式化。

所以我试试这个：

message("If you got to this point in the code, it means the matrix was empty. Calculation continues but you should consider re-evaluating an earlier step in the process")

这解决了我的代码标准 - 它少于80个字符行并且可以按预期重排。但是这会在我的消息输出中粘贴空格，我也不想要：

message("If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process")

所以我发现这个名为If you got to this point in the code, it means the matrix was empty. Calculation continues but you should consider re-evaluating an earlier step in the process的方便功能似乎解决了这个问题：

strwrap()

输出：

message(strwrap("If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process"))

看起来不错 - 但它消除了“考虑”和“重新评估”之间的空间，因为该空间处于换行符。

另一种选择是在代码中将其分解为块：

If you got to this point in the code, it means the matrix was empty. 
Calculation continues but you should considerre-evaluating an earlier 
step in the process

这使得输出看起来正确，但是文本不能再用IDE等轻松回流，因为它不是一个字符串，所以这对我在开发方面不起作用。

那么：我怎样才能制作一个格式正确的消息，让我可以轻松地跨行编写消息？

我写过这个函数：

message("If you got to this point in the code, it means ", 
"the matrix was empty. Calculation continues but you should consider ",
"re-evaluating an earlier step in the process")

使用内置是否有更好的方法，所以我不必在我写的每个R包中都包含这个函数？

Answer 1

使用来自strwrap的更多参数可以实现

message(strwrap(..., prefix = " ", initial = ""))

您可以通过播放参数的顺序来提高可读性。我不确定这是否更好。

message(strwrap(prefix = " ", initial = "", 
  "If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process"))

或者，如果你喜欢包装它

tidymess <- function(..., prefix = " ", initial = ""){
  message(strwrap(..., prefix = prefix, initial = initial))
}

Answer 2

您可以通过在字符串中添加\n来强制换行。

message("If you got to this point in the code,\nit means the matrix was empty.\nCalculation continues but you should consider re-evaluating\nan earlier step in the process")
# If you got to this point in the code,
# it means the matrix was empty.
# Calculation continues but you should consider re-evaluating
# an earlier step in the process

如何格式化多行R包邮件？

2 个答案: