问题
I have two datasets each that are monthly summaries of different variables for households. I want to merge the two based on the household ID and the month.
df1 one looks like this:
hh_ids date total
<chr> <chr> <dbl>
1 KELDK13 2013-8-1 1
2 KMOMB02 2013-2-1 1
3 KMOMB02 2013-5-1 2
4 KMOMB04 2013-7-1 2
5 KMOMB04 2013-9-1 1
6 KMOMB06 2013-6-1 1
7 KMOMB14 2013-8-1 1
8 KMOMB16 2013-6-1 1
9 KMOMB17 2012-10-1 1
10 KMOMB17 2012-11-1 2
and the first 10 rows of df2 looks like:
hh_ids date income consumption alcohol cleaning_materials clothing
1 KELDK01 2012-11-1 62.70588 40.52941 0 0.000000 0.000000
2 KELDK01 2012-12-1 17.64706 42.43530 0 1.058824 7.058824
3 KELDK01 2013-01-1 91.76471 48.23529 0 0.000000 0.000000
4 KELDK01 2013-02-1 91.76470 107.52940 0 0.000000 0.000000
5 KELDK01 2013-03-1 116.47060 114.47060 0 0.000000 0.000000
6 KELDK01 2013-04-1 124.41180 118.29410 0 2.705882 17.647060
7 KELDK01 2013-05-1 137.23530 105.00000 0 1.411765 1.882353
8 KELDK01 2013-06-1 131.52940 109.54120 0 4.352942 2.941176
9 KELDK01 2013-07-1 121.52940 113.47060 0 2.352941 25.882350
10 KELDK01 2013-08-1 123.32940 86.50588 0 2.588235 2.941176
I want the "total" column from to be added on as a column in df2 with the matched hh_ids and date.
I have tried to do the following:
df3<-merge(df2,df1,by=c("hh_ids","date"))
However, my df2 has 53 rows, and df1 has many more, and the resulting df3 only has 14 rows. Any suggestions would be much appreciated!
回答1:
If you want to retain all rows from your df2 even if they do not match to anything in df1 then you can use the all parameter in your merge:
df3 <- merge(df2, df1, by=c("hh_ids","date"), all.x=TRUE)
This is equivalent to doing a LEFT JOIN in SQL between df2 on the left and df1 on the right.
来源：https://stackoverflow.com/questions/38768197/merging-a-dataset-based-on-id-and-date