使用dplyr :: filter的tidyeval方法是什么? [英] What is the tidyeval way of using dplyr::filter?

问题描述

使用foo(c("b"))调用以下函数.输出显示为内联.

Call the function below using foo(c("b")). The outputs are shown inline.

写df %>% filter(!!x > (!!x))的正确方法是什么?

What is the right way of writing df %>% filter(!!x > (!!x))?

我提供了一个示例，该示例在tidyeval样式中使用mutate与filter进行对比.

I have included an example of using mutate in tidyeval style to contrast it with filter.

foo <- function(variables) {

  x <- rlang::sym(variables[[1]])

  print(x)
  #> b

  print(typeof(x))
  #> [1] "symbol"

  df <- data_frame(a = 1, b = 2)

  print(df %>% mutate(!!x := 100 + !!x))

  #> # A tibble: 1 x 2
  #>         a     b
  #>       <dbl> <dbl>
  #>   1     1   102  

  print(df %>% filter(!!x  > (!!x)))

  #> Error in !x : invalid argument type

  print(df %>% filter(magrittr::is_greater_than(!!x, !!x)))

  #> # A tibble: 0 x 2
  #> # ... with 2 variables: a <dbl>, b <dbl>

}

推荐答案

除了打字错误外，您大部分都在那儿，filter语句中的圆括号应该在变量上，而不是值上.

You are most of the way there except for a minor typo, the round brackets in your filter statement should be on the variable and not the value.

print(df %>% filter((!!x) > !!x))

#> # A tibble: 0 x 2
#> # ... with 2 variables: a <dbl>, b <dbl>

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