R dplyr左联接-多个返回值和新行:如何仅要求第一个匹配? [英] R dplyr left join - multiple returned values and new rows: how to ask for the first match only?

问题描述

比方说，我在单独的表格中列出了郊区名称，犯罪率及其理事会名称.

Let's say I have a list of suburb names, crime rate and their council names on a separate table.

我知道left_join(table1，table2，by = Suburb)将返回具有新添加的行的表，这是因为理事会的多个匹配项.问题在于，郊区3和4重叠成两个议会.

I know that left_join(table1, table2, by=Suburb) will return the table with newly added rows due to the multiple matches for council. The problem is that suburbs 3 and 4 overlap into two councils.

有没有办法只获得左联接只返回第一个匹配项，而不是创建新的行来促进多余的行?

Is there a way to only get the left join to only return the first match only rather than creating new rows to facilitate for the extra ones?

此外，在表2上，是否存在仅保留每个郊区的第一行并删除第二/第三/第四委员会重叠的第二/第三/第四实例的功能?

In addition, on Table 2, is there a function to only keep the first row of each suburb and remove the second/third/fourth instances where the second/third/fourth council overlapping occurs?

推荐答案

您可以使用plyr包和join()函数执行此操作.等效于left_join(table1，table2，by = Suburb)，但仅使用table2中的第一个Suburb匹配项是:join(table1，table2，by = Suburb，type ="left"，match ="first").尽管我很想知道自己，但我不确定dplyr软件包中的等效内容是什么.

You can do this using the plyr package and the join() function. The equivalent to left_join(table1, table2, by=Suburb) but only using the first Suburb match from table2 would be: join(table1, table2, by=Suburb, type="left", match="first"). I'm not sure what the equivalent is in the dplyr package, though I would love to know myself.

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