4
我需要按邏輯列(或者更準確地說,是否定)過濾表,但列的名稱可能會有所不同。這很容易,當我事先知道他們的名字:當列名存儲在字符串中時進行整齊評估
tb = tibble(
id = 1:4,
col1 = c(TRUE, TRUE, FALSE, FALSE),
col2 = c(TRUE, FALSE, TRUE, FALSE)
)
tb
## # A tibble: 4 x 3
## id col1 col2
## <int> <lgl> <lgl>
## 1 1 TRUE TRUE
## 2 2 TRUE FALSE
## 3 3 FALSE TRUE
## 4 4 FALSE FALSE
colname = quo(col1)
tb %>%
filter(!!colname) # rows where col1 is true
## # A tibble: 2 x 3
## id col1 col2
## <int> <lgl> <lgl>
## 1 1 TRUE TRUE
## 2 2 TRUE FALSE
tb %>%
filter(!(!!colname)) # rows where col1 is false
## # A tibble: 2 x 3
## id col1 col2
## <int> <lgl> <lgl>
## 1 3 FALSE TRUE
## 2 4 FALSE FALSE
colname = quo(col2)
tb %>%
filter(!!colname) # rows where col2 is true
## # A tibble: 2 x 3
## id col1 col2
## <int> <lgl> <lgl>
## 1 1 TRUE TRUE
## 2 3 FALSE TRUE
tb %>%
filter(!(!!colname)) # rows where col2 is false
## # A tibble: 2 x 3
## id col1 col2
## <int> <lgl> <lgl>
## 1 2 TRUE FALSE
## 2 4 FALSE FALSE
我不能,但是,弄清楚如何做同樣的當列名存儲在字符串。例如:
colname = "col1"
tb %>%
filter(!!colname)
## Error in filter_impl(.data, quo): Argument 2 filter condition does not evaluate to a logical vector
colname = quo("col1")
tb %>%
filter(!!colname)
## Error in filter_impl(.data, quo): Argument 2 filter condition does not evaluate to a logical vector
colname = quo(parse(text = "col1"))
tb %>%
filter(!!colname)
## Error in filter_impl(.data, quo): Argument 2 filter condition does not evaluate to a logical vector
所以,問題是,我該怎麼做呢?
編輯:這不是this question的重複,因爲從那以後用dplyr做非標準評估的首選方式已經改變。所有以_結尾的函數現在都已棄用,現在推薦使用整齊的評估框架。
[由(在dplyr)字符列名稱篩選數據幀(的可能的複製https://stackoverflow.com/questions/27197617/filter- data-frame-by-character-column-name-in-dplyr) – jdb
@jdb這裏提供的所有解決方案都使用不推薦使用的函數,內部語義從此改變。 –
[用dplyr使用字符串作爲輸入進行編程]的可能的副本(https://stackoverflow.com/questions/44121728/programming-with-dplyr-using-string-as-input) – aosmith