大于符号和定额产生错误 [英] Great than sign and quosure producing error

问题描述

在函数中使用dplyr时遇到问题。当基于一定数量进行过滤时，>符号似乎会导致不返回任何数据的问题。

I am encountering an issue when using dplyr in a function. When filtering based on a quosure, the > sign appears to cause an issue where no data are returned.

例如：

temp_df <- data.frame(
startdate_c = as.Date(c("2011-08-08", "2007-09-01", "2012-01-01", "2012-10-26", "2012-12-01", 
                "2016-01-01", "2006-06-01", "2009-04-01", "2005-02-09", "2004-08-01")),
enddate_c = as.Date(c("2011-08-14", "2012-09-04", "2014-06-06", "2014-02-28", "2013-04-05",  
              "2016-12-01", "2008-04-18", "2009-08-16", "2006-04-30", "2007-06-02")))

在这里，函数的简化版本：

Here's a stripped-down version of the function:

filter_f <- function(df, startdate = NULL, enddate = NULL) {

  if(!missing(startdate)) {
    start_var <- enquo(startdate)
  } else if("startdate_c" %in% names(df)) {
    start_var <- quo(startdate_c)
  } else {
    stop("No valid startdate found")
  }

  if(!missing(enddate)) {
    end_var <- enquo(enddate)
  } else if("enddate_c" %in% names(df)) {
    end_var <- quo(enddate_c)
  } else {
    stop("No valid enddate found")
  }

  df <- df %>%
    filter(!!start_var <= as.Date("2011-12-31") &
             !!end_var >= as.Date("2011-01-01"))

  return(df)
}

预期输出：

  startdate_c  enddate_c
1  2011-08-08 2011-08-14
2  2007-09-01 2012-09-04
3  2012-01-01 2014-06-06
4  2012-10-26 2014-02-28
5  2012-12-01 2013-04-05
6  2016-01-01 2016-12-01

相反，将返回一个空数据框。

Instead, an empty data frame is returned.

如果我调整代码并命名结尾日期而不是使用quasure，它起作用：

If I tweak the code and name the end date rather than using the quosure, it works:

filter_f2 <- function(df, startdate = NULL, enddate = NULL) {

  if(!missing(startdate)) {
    start_var <- enquo(startdate)
  } else if("startdate_c" %in% names(df)) {
    start_var <- quo(startdate_c)
  } else {
    stop("No valid startdate found")
  }

  if(!missing(enddate)) {
    end_var <- enquo(enddate)
  } else if("enddate_c" %in% names(df)) {
    end_var <- quo(enddate_c)
  } else {
    stop("No valid enddate found")
  }

  df <- df %>%
    filter(!!start_var <= as.Date("2011-12-31") &
             enddate_c >= as.Date("2011-01-01"))

  return(df)
}

创建开始日期和结束日期的代码是相同的，当我切换过滤器时，开始日期使用> =号，则出现了空df问题再次。这是dplyr中的错误还是我做错了什么？

The code to create the startdate and enddate quosures is identical, and when I switch the filter so the startdate has the >= sign, then the empty df issue arises again. Is this a bug in dplyr or am I doing something wrong?

推荐答案

这是一个操作顺序问题。比较运算符（< = 和> = ）的优先级高于！ 运算符。您需要

This is an order of operations problem. The comparison operators (<= and >=) have higher precedence than the ! operator. You need to do

  df <- df %>%
    filter((!!start_var) <= as.Date("2011-12-31") &
             (!!end_var) >= as.Date("2011-01-01"))

出于某种原因，单位似乎具有负值？观察

For some reason, quosues seem to have negative values? Observe

xvar <- quo(x)
quo(!!xvar <= 0)
# ~TRUE
quo(!!xvar >= 0)
# ~FALSE

比较...

quo((!!xvar) <= 0)
# ~(~x) <= 0
quo((!!xvar) >= 0)
# ~(~x) >= 0

最后（出于我不完全理解的原因）

And lastly (for reasons I don't fully understand)

quo(x) <= 4
# [1] TRUE
quo(x) >= 4
# [1] FALSE

似乎也与公式有关

(~x) <= 2
# [1] TRUE
(~x) >= 2
# [1] FALSE

这篇关于大于符号和定额产生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！