这是一个部分工作的解决方案,它包含一个SQL查询和dplyr
包中的mutate
函数。它没有解决连续行中多个NA值的情况,因为它是您的基本R解决方案的翻译,但它可能对其他(更完整的)方法有用。
我已经使用HiveQL的Lag and Lead函数来执行列向下移动和向上移动。它涉及创建一个新的辅助Spark表(example2),其中包含“Numb1”和“Numb2”列。然后,一旦辅助表已经创建,您可以用mutate
library(DBI)
library(sparklyr)
library(dplyr)
set.seed(1)
exampleDF <- data.frame (ID = 1:10, Cat = letters[1:5],
Numb = sample(c(NA, NA, NA, NA, 1:10), 10))
# Connection to Spark and creation of the table to test.
sc <- spark_connect("local")
example <- copy_to(sc, exampleDF)
# Create a Spark table with columns Numb1 and Numb2
DBI::dbSendQuery(sc, "CREATE TABLE example2 AS (SELECT ID, Cat, Numb, LAG(Numb, 1) over (PARTITION BY 1 ORDER BY ID) AS Numb1,
LEAD(Numb, 1) over (PARTITION BY 1 ORDER BY ID) AS Numb2 FROM exampledf)")
# Load the auxiliary table as a Spark DataFrame
ex2 <- tbl(sc, "example2")
# Mutate in order to create the Merged column
res <- ex2 %>%
mutate(Merged = ifelse(is.na(Numb), ifelse(is.na(Numb1), Numb2, Numb1), Numb))
res
# Source: lazy query [?? x 6]
# Database: spark_connection
id cat numb numb1 numb2 Merged
<int> <chr> <int> <int> <int> <int>
1 1 a NA NA 1 1
2 2 b 1 NA 3 1
3 3 c 3 1 6 3
4 4 d 6 3 NA 6
5 5 e NA 6 5 6
6 6 a 5 NA 4 5
7 7 b 4 5 9 4
8 8 c 9 4 10 9
9 9 d 10 9 NA 10
10 10 e NA 10 NA 10
作为一个侧面说明创建“合并”列中,您也可避免通过使用mutate
功能(以及所有ifelse
S) COALESCE
功能的手段。我认为这样会更有效率。
DBI::dbGetQuery(sc, "SELECT ID, Cat, Numb, COALESCE(Numb, Numb1, Numb2) AS Merged FROM example2")
ID Cat Numb Merged
1 1 a NA 1
2 2 b 1 1
3 3 c 3 3
4 4 d 6 6
5 5 e NA 6
6 6 a 5 5
7 7 b 4 4
8 8 c 9 9
9 9 d 10 10
10 10 e NA 10
我希望这会有所帮助。
EDITED
如果你想避免使用SQL可言,你可以用dplyr
功能做到这一点也:
example %>% arrange(ID) %>%
mutate(Numb1 = lag(Numb, 1)) %>%
mutate(Numb2 = lead(Numb, 1L)) %>%
mutate(Merged = ifelse(is.na(Numb), ifelse(is.na(Numb1), Numb2, Numb1), Numb))
# Source: lazy query [?? x 6]
# Database: spark_connection
# Ordered by: ID
ID Cat Numb Numb1 Numb2 Merged
<int> <chr> <int> <int> <int> <int>
1 1 a NA NA 1 1
2 2 b 1 NA 3 1
3 3 c 3 1 6 3
4 4 d 6 3 NA 6
5 5 e NA 6 5 6
6 6 a 5 NA 4 5
7 7 b 4 5 9 4
8 8 c 9 4 10 9
9 9 d 10 9 NA 10
10 10 e NA 10 NA 10
# ... with more rows
我遇到了一些麻烦的编码两个连续mutate
功能(这就是为什么我用首先是混合的SQL-dplyr方法)。我最终在sparklyr上打开了issue。
我认为滞后和领导是最有帮助的!谢谢Jaime! –
@KevinZheng不客气:-) –