在tidyeval（quo_name）

Question

我有两个功能：date_diff和group_stat。因此，我已阅读本文tidyverse，并尝试创建简单的函数并使用管道。

第一个函数创建一个difftime并将其命名为timex_minus_timey，但是当我将此结果传递到下一个函数中时，我必须查看名称，以便可以填写summary_var。有一个更好的方法吗？

library(tidyverse)
# 
set.seed(42)
data <- dplyr::bind_rows(
  tibble::tibble(Hosp = rep("A", 1000),
                 drg = sample(letters[1:5], 1000, replace = TRUE),
                 time1 = as.POSIXlt("2018-02-03 08:00:00", tz = "UTC") + rnorm(1000, 0, 60*60*60),
                 time2 = time1 + runif(1000, min = 10*60, max = 20*60)),

  tibble::tibble(Hosp = rep("B", 1000),
                 drg = sample(letters[1:5], 1000, replace = TRUE),
                 time1 = as.POSIXlt("2018-02-03 08:00:00", tz = "UTC") + rnorm(1000, 0, 60*60*60),
                 time2 = time1 + runif(1000, min = 10*60, max = 20*60))
)



date_diff <- function(df, stamp1, stamp2, units = "mins"){

  stamp1 <- rlang::enquo(stamp1)
  stamp2 <- rlang::enquo(stamp2)

  name <- paste0(rlang::quo_name(stamp1), "_minus_", rlang::quo_name(stamp2))

  out <- df %>%
    dplyr::mutate(!!name := as.numeric(difftime(!!stamp1, !!stamp2, units=units)))

  out
}


group_stat <- function(df, group_var, summary_var, .f) {

  func <- rlang::as_function(.f)

  group_var <-  rlang::enquo(group_var)
  summary_var <-rlang::enquo(summary_var)

  name <- paste0(rlang::quo_name(summary_var), "_", deparse(substitute(.f)))

  df %>%
    dplyr::group_by(!!group_var) %>%
    dplyr::summarise(!!name := func(!!summary_var, na.rm = TRUE))
}


data %>% 
  date_diff(time2, time1) %>%  
  group_stat(Hosp, summary_var = time2_minus_time1, mean)
#> # A tibble: 2 x 2
#>   Hosp  time2_minus_time1_mean
#>   <chr>                  <dbl>
#> 1 A                       15.1
#> 2 B                       14.9

^{由reprex package（v0.2.1）于2019-05-02创建}

Answer 1

如果您打算始终以这种方式一个接一个地使用这些功能，则可以使用date_diff添加一个包含新列名称的属性，并让group_stat使用该属性。在if条件下，仅当属性存在且未提供summary_var参数时才使用该属性。

date_diff <- function(df, stamp1, stamp2, units = "mins"){

  stamp1 <- rlang::enquo(stamp1)
  stamp2 <- rlang::enquo(stamp2)

  name <- paste0(rlang::quo_name(stamp1), "_minus_", rlang::quo_name(stamp2))

  out <- df %>%
    dplyr::mutate(!!name := as.numeric(difftime(!!stamp1, !!stamp2, units=units)))

  attr(out, 'date_diff_nm') <- name
  out
}


group_stat <- function(df, group_var, summary_var, .f) {
  if(!is.null(attr(df, 'date_diff_nm')) & missing(summary_var))
      summary_var <- attr(df, 'date_diff_nm')

  group_var <-  rlang::enquo(group_var)
  name <- paste0(summary_var, "_", deparse(substitute(.f)))

  df %>%
    dplyr::group_by(!!group_var) %>% 
    dplyr::summarise_at(summary_var, funs(!!name := .f), na.rm = T)
}


data %>% 
  date_diff(time2, time1) %>% 
  group_stat(Hosp, .f = mean)

# # A tibble: 2 x 2
#   Hosp  time2_minus_time1_mean
#   <chr>                  <dbl>
# 1 A                       15.1
# 2 B                       14.9