使用标准评估从 tidyr 包中从 Gather() 中排除列 [英] Excluding column from gather() from tidyr package using standard evaluation
问题描述
我正在尝试使用标准评估从 tidyr 包中排除 gather()
中的列.
I'm trying to exclude a column from gather()
from the tidyr package using standard evaluation.
使用非标准评估,这可以正常工作:
Using non-standard evaluation, this works fine:
mtcars_df <- head(mtcars[, c("mpg", "hp", "cyl")])
tidyr::gather(mtcars_df, key, val, -cyl)
但是,使用标准评估,以下两种方法都不起作用并且都返回错误:
However, using standard evaluation, neither of the following work and both return an error:
tidyr::gather_(mtcars_df, "key", "val", -"cyl")
tidyr::gather_(mtcars_df, "key", "val", -cyl)
作为一种解决方法,我尝试使用 select()
辅助函数 contains()
,但这只是返回了原始的 data.frame
, mtcars_df
:
As a work-around, I tried to use the select()
helper function contains()
, but this just returned the original data.frame
, mtcars_df
:
tidyr::gather_(mtcars_df, "key", "val", -dplyr::contains("cyl"))
如何使用标准评估以这种方式排除列?这是怎么回事?
How can I exclude a column in this way using standard evaluation? What's going on here?
推荐答案
根据 tidyr github issue #109:gather_ 不再支持删除列?、
According to tidyr github issue #109: gather_ no longer supports dropping a column?,
gather_() 仅适用于字符向量.- 哈德利·威克姆,2015 年
gather_() only works with character vectors. - Hadley Wickham, 2015
你可以试试
library(dplyr)
mtcars_df %>% tidyr::gather_("key", "val", setdiff(names(.), "cyl"))
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