R reshape2'聚合函数丢失:默认为长度'

Question

我已经在SO上多次看过这次重塑2但是没有找到解决我特定问题的方法;

我有这样的数据集;

head(data)
student    test    score
Adam      Exam1     80
Adam      Exam2     90
John      Exam1     70
John      Exam2     60

我试图将其转换为看起来像这样的宽格式;

Student    Exam1    Exam2 ........ ExamX
Adam         80       90
John         70       60

使用;

dcast(data,student~test,value.var='score')

但数据最终看起来像这样的东西;

Student    Exam1     Exam2
Adam        0          0
John        0          1

有这个错误;

Aggregation function missing: defaulting to length

任何想法为什么它将所有这些值更改为(0或1)？

Answer 1

感谢@akrun指出了这一点.

那么,您的数据很可能有重复的行,看起来像这样:

student    test    score
Adam      Exam1     80
Adam      Exam1     85
Adam      Exam2     90
John      Exam1     70
John      Exam2     60

或者像这样:

student   class     test    score
Adam      Biology   Exam1     80
Adam      Theology  Exam1     85
Adam      Theology  Exam2     90
John      Biology   Exam1     70
John      Theology  Exam2     60

当你像这样投射: dcast(data, student + class ~ test, value.var='score')