R 创建函数返回的所有消息、警告和错误的列表

发布于08月18日

我在R中有一个调用其他函数的函数.有时，这些函数可能会返回相同的消息.我只想把这条消息打印一次.处理这一问题的最好方法是什么？

在下面的示例中，functionC将打印"the value is 5".两次，如果b和c的自变量是5.我只想打印一次.

functionA <- function(a){
  
  if(a==5){
    message("The value is 5.")
  }
  return(a-2)
}

functionB <- function(b){
  
  if(b==5){
    message("The value is 5.")
  }
  return(b+7)
}

functionC <- function(a,b){
  a <- functionA(a)
  b <- functionB(b)
  c <- rbind(a,b)
  return(c)
}

functionC(5,5)

推荐答案

您可以使用withCallingHandlers来实时捕获(和 suppress )消息，然后使用unique来减少它们，然后重新将它们释放出来.为了透明起见，重复使用时我会加上(n times)(否则您可能不清楚内部调用有多吵).

functionC <- function(a,b){
  msgs <- character(0)
  a <- withCallingHandlers(
    functionA(a),
    message = function(m) {
      msgs <<- c(msgs, conditionMessage(m))
      invokeRestart("muffleMessage")
    })
  b <- withCallingHandlers(
    functionB(b),
    message = function(m) {
      msgs <<- c(msgs, conditionMessage(m))
      invokeRestart("muffleMessage")
    })
  msgs <- trimws(msgs)
  # since 'table' does not preserve the original order, we'll do a few
  # extra steps to ensure the messages appear in the order of their
  # _first_ appearance
  counts <- table(msgs)
  counts <- counts[match(names(counts), msgs)]
  msgs <- paste0(names(counts), ifelse(counts > 1, sprintf(" (%d times)", counts), ""))
  for (m in msgs) message(m)
  c <- rbind(a, b)
  return(c)
}
functionC(5,5)
# The value is 5. (2 times)
#   [,1]
# a    3
# b   12

您可以重复message=/"muffleMessage"和warning=/"muffleWarning"来捕捉警告...不过，您也可以使用purrr::quietly:

functionC2 <- function(a,b){
  msgs <- character(0)
  warns <- character(0)
  aout <- purrr::quietly(functionA)(a)
  bout <- purrr::quietly(functionB)(b)
  fewer <- function(z) {
    z <- trimws(z)
    counts <- table(z)
    counts <- counts[match(names(counts), z)]
    paste0(names(counts), ifelse(counts > 1, sprintf(" (%d times)", counts), ""))
  }
  msgs <- fewer(c(aout$messages, bout$messages))
  warns <- fewer(c(aout$warnings, bout$warnings))
  cout <- rbind(aout$result, bout$result)
  for (m in msgs) message(m)
  for (w in warns) warning(w)
  return(cout)
}