在dataframe中的特定位置创建列

Question

我想在特定位置创建一个新变量.我可以创建变量mutate然后重新排序,select但我宁愿选择tibble:add_column这样做的方式.

这是iris数据集的一个简单示例:

library(tidyverse)
## This works fine
iris %>% mutate(With_mutate = ifelse(Sepal.Length > 4 & Sepal.Width > 3 , TRUE, FALSE)) %>% 
         select(Sepal.Length:Petal.Width, With_mutate, everything()) %>%
         head()

## This works also
iris %>% add_column(With_add_column = "Test", .before = "Species") %>%
head()

## This doesn't work
iris %>% add_column(With_add_column = ifelse(Sepal.Length > 4 & Sepal.Width > 3 , TRUE, FALSE), .before = "Species") %>%
head()
Error in ifelse(Sepal.Length > 2 & Sepal.Width > 1, TRUE, FALSE) :
  object 'Sepal.Length' not found

如果有人能告诉我为什么我的ifelse陈述无效,我将不胜感激add_column.

Answer 1

原因是mutate或者summarise等等根据指定符号得到列值,但是这里add_column不会.因此,我们可以提取列.$

iris %>% 
   add_column(With_add_column = ifelse(.$Sepal.Length > 4 & 
                                 .$Sepal.Width > 3 , TRUE, FALSE), .before = "Species") %>%
   head()
#Sepal.Length Sepal.Width Petal.Length Petal.Width With_add_column Species
#1          5.1         3.5          1.4         0.2            TRUE  setosa
#2          4.9         3.0          1.4         0.2           FALSE  setosa
#3          4.7         3.2          1.3         0.2            TRUE  setosa
#4          4.6         3.1          1.5         0.2            TRUE  setosa
#5          5.0         3.6          1.4         0.2            TRUE  setosa
#6          5.4         3.9          1.7         0.4            TRUE  setosa

只是为了使它紧凑,逻辑条件的值是TRUE/FALSE这样的,我们不需要一个ifelseie

add_column(With_add_column = .$Sepal.Length > 4 & .$Sepal.Width > 3, .before = "Species")

可以取代第二步