r - 如何合并具有相同列名的多个数据框？

Question

是)我有的:

我有一个具有以下各列的“主”数据框:

userid, condition

由于有四个实验条件，因此我也有四个带有答案信息的数据框，其中包括以下几列:

userid, condition, answer1, answer2

现在，我想加入这些内容，以便合并用户ID，条件及其对这些条件的答案的所有组合。每个条件在每行的相应列中应仅具有正确的答案。

简短的独立示例:

master = data.frame(userid=c("foo","foo","foo","foo","bar","bar","bar","bar"), condition=c("A","B","C","D","A","B","C","D"))
cond_a = data.frame(userid=c("foo","bar"), condition="A", answer1=c("1","1"), answer2=c("2","2"))
cond_b = data.frame(userid=c("foo","bar"), condition="B", answer1=c("3","3"), answer2=c("4","4"))
cond_c = data.frame(userid=c("foo","bar"), condition="C", answer1=c("5","5"), answer2=c("6","6"))
cond_d = data.frame(userid=c("foo","bar"), condition="D", answer1=c("7","7"), answer2=c("8","8"))

如何将所有条件合并到主数据库中，所以主数据库表如下所示？

  userid condition answer1 answer2
1    bar         A       1       2
2    bar         B       3       4
3    bar         C       5       6
4    bar         D       7       8
5    foo         A       1       2
6    foo         B       3       4
7    foo         C       5       6
8    foo         D       7       8

我尝试了以下方法:

temp = merge(master, cond_a, all.x=TRUE)

这给了我:

  userid condition answer1 answer2
1    bar         A       1       2
2    bar         B    <NA>    <NA>
3    bar         C    <NA>    <NA>
4    bar         D    <NA>    <NA>
5    foo         A       1       2
6    foo         B    <NA>    <NA>
7    foo         C    <NA>    <NA>
8    foo         D    <NA>    <NA>

但是，只要我这样做...

merge(temp, cond_b, all.x=TRUE)

没有条件B的值。怎么来的？

  userid condition answer1 answer2
1    bar         A       1       2
2    bar         B    <NA>    <NA>
3    bar         C    <NA>    <NA>
4    bar         D    <NA>    <NA>
5    foo         A       1       2
6    foo         B    <NA>    <NA>
7    foo         C    <NA>    <NA>
8    foo         D    <NA>    <NA>

Answer 1

您可以按以下方式使用Reduce()和complete.cases():

merged <- Reduce(function(x, y) merge(x, y, all=TRUE), 
                 list(master, cond_a, cond_b, cond_c, cond_d))
merged[complete.cases(merged), ]
#    userid condition answer1 answer2
# 1     bar         A       1       2
# 2     bar         B       3       4
# 4     bar         C       5       6
# 6     bar         D       7       8
# 8     foo         A       1       2
# 9     foo         B       3       4
# 11    foo         C       5       6
# 13    foo         D       7       8

Reduce()可能需要一些习惯。您定义函数，然后提供对象的list以重复将函数应用于该函数。因此，该语句就像在做:

temp1 <- merge(master, cond_a, all=TRUE)
temp2 <- merge(temp1, cond_b, all=TRUE)
temp3 <- merge(temp2, ....)

或类似的东西:

merge(merge(merge(master, cond_a, all=TRUE), cond_b, all=TRUE), cond_c, all=TRUE)

complete.cases()创建一个逻辑向量，以确定指定的列是否“完整”；该逻辑向量可用于从合并的data.frame中子集化。