在SparkR shell 1.5.0中,创建了一个示例数据集:
df_test <- createDataFrame(sqlContext, data.frame(mon = c(1,2,3,4,5), year = c(2011,2012,2013,2014,2015)))
df_test1 <- createDataFrame(sqlContext, data.frame(mon1 = c(1,2,3,4,5,6,7,8)))
df_test2 <- join(df_test1, df_test, joinExpr = df_test1$mon1 == df_test$mon, joinType = "left_outer")
数据集:df_test2
+----+----+------+
|mon1| mon| year|
+----+----+------+
| 7.0|null| null|
| 1.0| 1.0|2011.0|
| 6.0|null| null|
| 3.0| 3.0|2013.0|
| 5.0| 5.0|2015.0|
| 8.0|null| null|
| 4.0| 4.0|2014.0|
| 2.0| 2.0|2012.0|
+----+----+------+
问题:如果有null
我怎样才能将它替换为0
在列中df_test2$year
或者使用默认值?
输出应该是这样的,
+----+----+------+
|mon1| mon| year|
+----+----+------+
| 7.0|null| 0 |
| 1.0| 1.0|2011.0|
| 6.0|null| 0 |
| 3.0| 3.0|2013.0|
| 5.0| 5.0|2015.0|
| 8.0|null| 0 |
| 4.0| 4.0|2014.0|
| 2.0| 2.0|2012.0|
+----+----+------+
我用过otherwise/when
,但不起作用
df_test2$year <- otherwise(when(isNull(df_test2$year), 0 ), df_test2$year)
它抛出了错误,
Error in rep(yes, length.out = length(ans)) :
attempt to replicate an object of type 'environment'