在case_when（）中抛出错误 [英] throw an error inside a case_when()

问题描述

我在 mutate（）中有一个 case_when（），我希望R停止并抛出如果满足 TRUE 条件，则为错误。这是出于调试目的。

I have a case_when() inside a mutate() and I'd like R to stop and throw an error if the TRUE condition is fulfilled. This is for debugging purposes.

例如，mtcars $ cyl的值为4、6或8。在第四行有适当的解决方案后，这应该是能够正常运行：

For example, values for mtcars$cyl are 4, 6 or 8. With the proper solution in place in the fourth line, this should be able to run without error:

mtcars %>%
  mutate(test = case_when(
    cyl > 3 ~ "ok",
    TRUE ~ # code for throwing error here
  ))

这应该引发错误：

mtcars %>%
  mutate(test = case_when(
    cyl < 3 ~ "ok",
    TRUE ~ # code for throwing error here
  ))

我尝试了停止，但这会触发异常，即使 TRUE 从未实现。

I tried stop but this triggers the exception even if TRUE is never fulfilled.

推荐答案

在 case_when 调用中，您无法执行此操作据我了解，因为所有RHS都会经过预先评估，以确保它们属于同一类型。

You can't do it in the case_when call as far as I understand, because all RHSs will be evaluated beforehand to make sure they're of the same type.

但是您可以这样做：

mtcars %>%
  mutate(test = case_when(
    cyl > 3 ~ "ok",
    TRUE ~ NA_character_
  ),
  test=if (anyNA(test)) stop() else test
  )

或

mtcars %>%
  mutate(test = case_when(
    cyl > 3 ~ "ok",
    TRUE ~ "STOP_VALUE"
  ),
  test=if ("STOP_VALUE" %in% test) stop() else test
  )

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