如何使用 purrr::possibility 来捕捉绘图错误 [英] How to use purrr::possibly to catch plot errors

问题描述

我尝试编写一个可以安全"运行其他函数的函数.这里的安全只是意味着如果某些绘图功能失败，我不希望脚本失败.简单例子:

库(ggplot2)图书馆(咕噜咕噜)## 函数我以为我可以用来安全地运行其他函数safe_plot <- function(.FUN, ...) {safe_fun <- purrr::possably(.f = .FUN, 否则 = NULL)safe_fun(...)}## 简单的绘图功能plot_fun <- 函数(df){df%＞%ggplot(aes(xvar, yvar)) +geom_point()}## 适用于良好的数据some_data <- data.frame(xvar = 1:10, yvar = 1:10)safe_plot(.FUN = plot_fun, df = some_data)

## 适用于未定义的数据:>safe_plot(.FUN = plot_fun, df = not_defined)空值## 为空数据框而跌倒empty_data <- data.frame()>safe_plot(.FUN = plot_fun, df = empty_data)FUN(X[[i]], ...) 中的错误:找不到对象xvar"

我想要的是一个通用函数，我可以将绘图函数传递给它 - 如果发生错误 - 不会停止脚本.例如，我知道我可以执行以下操作:

## 带检查的简单绘图函数plot_fun <- 函数(df){如果(nrow(df)> 0){df%＞%ggplot(aes(xvar, yvar)) +geom_point()}}

但在这里，我更感兴趣的是了解为什么 purrr::possibility 没有发现错误以及解决此问题的更好方法……假设我不在乎可能导致错误的原因.

解决方案

可以直接使用tryCatch.
在任何一种情况下，possably 和最终 tryCatch 都没有捕获到错误的原因是

<预><代码>empty_data <- data.frame()safe_plot(.FUN = plot_fun, df = empty_data)#>空值

I tried to write a function which would run other functions "safely". By safely here I just mean I don't want scripts to fall over if some plot functions fail. Simple example:

library(ggplot2)
library(purrr)

## function I thought I could use to run other functions safely
safe_plot <- function(.FUN, ...) {
  safe_fun <- purrr::possibly(.f = .FUN, otherwise = NULL)
  safe_fun(...)
}

## Simple plot function
plot_fun <- function(df) {
  df %>% 
    ggplot(aes(xvar, yvar)) +
    geom_point()
}

## Works for good data
some_data <- data.frame(xvar = 1:10, yvar = 1:10)
safe_plot(.FUN = plot_fun, df = some_data)

## Works here for data that is not defined:
> safe_plot(.FUN = plot_fun, df = not_defined)
NULL

## Falls over for an empty data frame
empty_data <- data.frame()
> safe_plot(.FUN = plot_fun, df = empty_data)
Error in FUN(X[[i]], ...) : object 'xvar' not found

What I would like is a generic function that I can pass plot functions to which - if an error occurs - won't stop a script. I know I could do the following for example:

## Simple plot function with check
plot_fun <- function(df) {
  if (nrow(df) > 0) {
    df %>%
      ggplot(aes(xvar, yvar)) +
      geom_point()
  }
}

But here I'm more interested in learning about why purrr::possibly did not catch the error and a perhaps a better way to go about this problem...assuming I don't care what may have caused an error.

解决方案

You could directly use tryCatch.
In either cases, the reason for the error not being catched by possibly and eventually tryCatch is due to the lazy evaluation of print.ggplot which occurs outside tryCatch.
Solution is to force print() into tryCatch():

library(ggplot2)

safe_plot <- function(.FUN, ...) {
  tryCatch(print(.FUN(...)),error = function(e) NULL)
}

## Simple plot function
plot_fun <- function(df) {
  df %>% 
    ggplot(aes(xvar, yvar)) +
    geom_point() 
}


## Works for good data
some_data <- data.frame(xvar = 1:10, yvar = 1:10)
safe_plot(.FUN = plot_fun, df = some_data)
#> NULL

empty_data <- data.frame()
safe_plot(.FUN = plot_fun, df = empty_data)
#> NULL

这篇关于如何使用 purrr::possibility 来捕捉绘图错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！