Dataset HAVE
是来自以下字符的电话呼叫数据的 tibble 边缘列表Recess:
Student Friend nCalls
TJ Spinelli 3
TJ Gretchen 7
TJ Gus 6
TJ Vince 8
TJ King Bob 1
TJ Mikey 2
Spinelli TJ 3
Spinelli Vince 2
Randall Ms. Finster 17
Dataset NEED
包括来自的所有原始列HAVE
但包含一个新变量,nCallsPerStudent
,这正是它听起来的样子:
Student Friend nCalls nCallsPerStudent
TJ Spinelli 3 27
TJ Gretchen 7 27
TJ Gus 6 27
TJ Vince 8 27
TJ King Bob 1 27
TJ Mikey 2 27
Spinelli TJ 3 5
Spinelli Vince 2 5
Randall Ms. Finster 17 17
我如何从HAVE
to NEED
?
我们可以按“学生”分组mutate
创建新列
library(dplyr)
df %>%
group_by(Student) %>%
mutate(nCallsPerStudent = sum(nCalls))
或者使用base R
df$nCallsPerStudent <- with(df, ave(nCalls, Student, FUN = sum))
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