R函数返回值以及警告消息 [英] R function return value as well warning message

问题描述

我调用了其他的lib函数，它进行计算并抛出警告消息。我尝试使用tryCatch（）来捕获消息，但不知道如何保留计算值和警告消息。这里是示例（简化）代码，我希望mydiv函数具有计算值和警告消息。现在mydiv调用将返回除法值或警告，但不是两者。

I called other lib function, which does the calculation and throws warning message. I tried to use tryCatch() to capture the message but do not know how to keep the calculated value and the warning message. Here is sample (simplified) code, I would like mydiv function has both calculated value and warning message. Right now mydiv calls will return the division value or the warning but not both.

mydiv = function(x, y){  
tryCatch({
# raise warning message
if (x > y)
  warning("throw a warning")
  # function calc result
  x/y
}, 
warning = function(war) {
flag = paste("DIV Warning:", war$message)
return (flag)
},
error = function(err) {
 flag = paste("DIV Err", err)   
 return (flag)
})
}

如果我调用x = mydiv（2,1），那么x的值为DIV Warning：throw a warning;如果x = mydiv（2,4），则x：[1] 0.5。
所以我的问题是：1.使用tryCatch：如果可能的话如何返回计算的值和警告消息; 2.是否有更好的方法从函数中获取这两个值。

If I call x = mydiv(2, 1) then the x has value "DIV Warning: throw a warning"; if x = mydiv(2, 4) then x: [1] 0.5. So my question is: 1. use tryCatch: how to return the calculated value and warning message if possible; 2. whether there is a better approach to get both values from a function.

推荐答案

您可以使用内置的警告函数作为如下：

You could use the built in warning function as in the following:

mydiv = function(x, y){  
  if (x > y)
    warning("throw a warning")
  # function calc result
  return(x/y)
}

如果您想要返回警告而不是将其作为警告消息发出，则可以返回一个指定列表，如果未生成警告，则列表中的警告条目将为NA ：

If you want to return a warning instead of emitting it as a warning message, you could return a named list, where the warning entry in the list will be NA if no warning is generated:

mydiv = function(x, y){
  warn <- NA  
  if (x > y)
    warn <- "throw a warning"
  # function calc result
  return(list(value=x/y, warning=warn))
}

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