如何在 R 中使用由另一列分组的聚合列值创建一个新数据框

Question

我之前使用 dplyr 成功添加了聚合列，但我不确定如何创建一个新的宽数据框，该数据框包含基于另一列 (SkillGroup) 的值的新聚合列 (平均值) 并按另一列 (EmployeeID)。

我原来的 DF 是这样的：

EmployeeID <- c(rep(1,5), rep(2,3))
SkillGroup <- c(rep("A",3), rep("B",2), "A", "B", "C")
Proficiency <- c(1,2,3,4,5,1,2,3)
mydata <- data.frame(EmployeeID, SkillGroup, Proficiency)

我感兴趣的最终数据框如下所示：

EmployeeID2 <- c(1,2)
MeanSkillA <- c(2,1)
MeanSkillB <- c(4.5,2)
MeanSkillC <- c(NA, 3)
desiredDF <- data.frame(EmployeeID2, MeanSkillA, MeanSkillB, MeanSkillC)

Answer 1

聚合值然后tidyr::spread:

mydata %>% 
    group_by(EmployeeID, SkillGroup = paste('MeanSkill', SkillGroup, sep="")) %>% 
    summarise(MeanSkill = mean(Proficiency)) %>% 
    spread(SkillGroup, MeanSkill)

# A tibble: 2 x 4
# Groups:   EmployeeID [2]
#  EmployeeID MeanSkillA MeanSkillB MeanSkillC
#*      <dbl>      <dbl>      <dbl>      <dbl>
#1          1          2        4.5         NA
#2          2          1        2.0          3