r - 函数从字面上接受一个参数而不是参数的值

Question

我尝试创建一个函数，该函数将根据每个人拥有的唯一 PATIENT_ID 数量按降序返回 x 最大分子。从某个日期到最后一个日期。

data <- data.frame(PATIENT_ID = c(1,1,2,2), dateM = c(ymd("2020-01-05","2020-01-06","2020-05-06","2019-12-15")), MOLECULES = c("mol1", "mol1", "mol1", "mol2"))


topx <- function(data, datefrom, var ,  x = 5){
  data %>%
  subset(dateM >= datefrom) %>%
  group_by(var) %>%
  summarize(pat = length(unique(PATIENT_ID))) %>%
  arrange(-pat) %>% 
  head(x) %>% 
  select(1)
}

topx(data = data, datefrom = "2016-04", var = MOLECULES, x = 2) 

在这种情况下，想要的结果是:

c("mol1","mol2")

但是，它将 var 作为文本并且不解析 MOLECULES 并告诉我。

 Error: Must group by variables found in `.data`.
* Column `var` is not found.

Answer 1

很酷的功能。用dplyr编程时有一些特殊的规则和操作.查看更多 here .具体来说，您需要 {{}}运算符(operator)。

library(tidyverse)
library(lubridate)
#> 
#> Attaching package: 'lubridate'
#> The following objects are masked from 'package:base':
#> 
#>     date, intersect, setdiff, union

data <- data.frame(PATIENT_ID = c(1,1,2,2), dateM = c(ymd("2020-01-05","2020-01-06","2020-05-06","2019-12-15")), MOLECULES = c("mol1", "mol1", "mol1", "mol2"))

topx <- function(data, datefrom, var ,  x = 5){
  data %>%
    subset(dateM >= datefrom) %>%
    group_by({{var}}) %>%
    summarize(pat = length(unique(PATIENT_ID))) %>%
    arrange(-pat) %>% 
    head(x) %>% 
    select(1)
}

topx(data = data, datefrom = "2016-04-01", var = MOLECULES, x = 2) 
#> `summarise()` ungrouping output (override with `.groups` argument)
#> # A tibble: 2 x 1
#>   MOLECULES
#>   <chr>    
#> 1 mol1     
#> 2 mol2

创建于 2021-01-14 由 reprex package (v0.3.0)