使用 purrr 创建数据框列表以选择列

Question

这些是我的数据：

set.seed(1234321)

# Original dataframe (i.e. a questionnaire survey data)
answer <- c("Yes", "No")
likert_scale <- c("strongly disagree", "disagree", "undecided", "agree", "strongly agree")
d1 <- c(rnorm(10)*10)
d2 <- sample(x = c(letters), size = 10, replace = TRUE)
d3 <- sample(x = likert_scale, size = 10, replace = TRUE)
d4 <- sample(x = likert_scale, size = 10, replace = TRUE)
d5 <- sample(x = likert_scale, size = 10, replace = TRUE)
d6 <- sample(x = answer, size = 10, replace = TRUE)
d7 <- sample(x = answer, size = 10, replace = TRUE)
original_df <- data.frame(d1, d2, d3, d4, d5, d6, d7)

# Questionnaire codebook 
quest_section <- c("generic", "likert scale", "specific approval")
starting_column <- c(1, 3, 6)
ending_column <- c(2, 5, 7)
df_codebook <- data.frame(quest_section, starting_column, ending_column)

我想获得以下数据框列表：

> my_df_list
$generic
           d1 d2
1   12.369081  z
2   15.616230  x
3   18.396185  f
4    3.173245  q
5   10.715115  j
6  -11.459955  p
7    2.488894  j
8    1.158625  n
9   26.200816  a
10  12.624048  b

$`likert scale`
                  d3                d4                d5
1           disagree    strongly agree    strongly agree
2          undecided         undecided strongly disagree
3     strongly agree         undecided strongly disagree
4              agree         undecided         undecided
5  strongly disagree             agree         undecided
6           disagree strongly disagree         undecided
7           disagree             agree          disagree
8           disagree strongly disagree         undecided
9          undecided strongly disagree          disagree
10 strongly disagree          disagree    strongly agree

$`specific approval`
    d6  d7
1   No  No
2   No  No
3  Yes  No
4  Yes Yes
5  Yes Yes
6  Yes Yes
7  Yes  No
8   No Yes
9   No  No
10  No Yes

为了使用purrr方法获得先前的结果，我执行了以下代码：

my_list_2 <- pmap(list(c(1:3)), ~dplyr::select(original_df,df_codebook[,2]:df_codebook[,3])) %>% 
        set_names(df_codebook[,1])

但结果是这样的：

> my_list_2
$generic
           d1 d2
1   12.369081  z
2   15.616230  x
3   18.396185  f
4    3.173245  q
5   10.715115  j
6  -11.459955  p
7    2.488894  j
8    1.158625  n
9   26.200816  a
10  12.624048  b

$`likert scale`
           d1 d2
1   12.369081  z
2   15.616230  x
3   18.396185  f
4    3.173245  q
5   10.715115  j
6  -11.459955  p
7    2.488894  j
8    1.158625  n
9   26.200816  a
10  12.624048  b

$`specific approval`
           d1 d2
1   12.369081  z
2   15.616230  x
3   18.396185  f
4    3.173245  q
5   10.715115  j
6  -11.459955  p
7    2.488894  j
8    1.158625  n
9   26.200816  a
10  12.624048  b

我刚刚获得了一个类似问题的解决方案，但现在我有兴趣使用和理解purrr方法来执行它。

Answer 1

如果你想使用purrr你可以试试这个：

library(purrr)

my_list <- map2(.x = df_codebook$starting_column, 
                .y = df_codebook$ending_column, 
                ~ original_df[, .x:.y]) %>%
  set_names(df_codebook$quest_section)

map2允许您迭代两个输入 - 在这种情况下，开始和结束列。

> my_list
$generic
           d1 d2
1   12.369081  z
2   15.616230  x
3   18.396185  f
4    3.173245  q
5   10.715115  j
6  -11.459955  p
7    2.488894  j
8    1.158625  n
9   26.200816  a
10  12.624048  b

$`likert scale`
                  d3                d4                d5
1           disagree    strongly agree    strongly agree
2          undecided         undecided strongly disagree
3     strongly agree         undecided strongly disagree
4              agree         undecided         undecided
5  strongly disagree             agree         undecided
6           disagree strongly disagree         undecided
7           disagree             agree          disagree
8           disagree strongly disagree         undecided
9          undecided strongly disagree          disagree
10 strongly disagree          disagree    strongly agree

$`specific approval`
    d6  d7
1   No  No
2   No  No
3  Yes  No
4  Yes Yes
5  Yes Yes
6  Yes Yes
7  Yes  No
8   No Yes
9   No  No
10  No Yes