R 数据帧内和跨时间重复观测和因子组合的计数函数

假设我有以下类型的数据：

df <- data.frame(student = c("S1", "S2", "S3", "S4", "S5", "S2", "S6", "S1", "S7", "S8"), 
              factor = c("A", "A", "A", "A", "A", "B", "B", "C", "C", "D"), 
              year =  c(1, 1, 1, 1, 1, 1, 1, 2, 2, 2), 
              count1 = c(0, 1, 0, 0, 0, 1, 0, 0, 0, 0), 
              count2 = c(1, 0, 0, 0, 0, 0, 0, 1, 0, 0))

---

df这里有一系列命令，可以让你达到目的，使用因素交互作用来查找学生在同一年中的因素变化：

# Add up the occurrences of a student having multiple factors in the same year,
# for each year
in.each.year <- aggregate(factor~student:year, data=df, FUN=function(x) length(x)-1)[c(1,3)]

# Total these up, for each student
in.year <- aggregate(factor~student, data=in.each.year, FUN=sum)

# The name was "factor".  Set it to the desired name.
names(in.year)[2] <- 'count1'

# Find the occurrences of a student having multiple factors
both <- aggregate(factor~student, data=df, FUN=function(x) length(x)-1)
names(both)[2] <- 'both'

# Combine with 'merge'
m <- merge(in.year, both)

# Subtract to find "count2"
m$count2 <- m$both - m$count1
m$both <- NULL

m
##   student count1 count2
## 1      S1      0      1
## 2      S2      1      0
## 3      S3      0      0
## 4      S4      0      0
## 5      S5      0      0
## 6      S6      0      0
## 7      S7      0      0
## 8      S8      0      0

没有样本数据很难理解这个问题。请在这里为好的人添加可复制的样品以帮助您。请参见编辑以显示模拟数据的代码。两条注释。1（有点小）：在
apply
变得过于昂贵之前，10K的观测值与您需要的相差甚远。2（有点大）：你想要什么还不完全清楚。更改您的示例数据，以便某些学生实际获得0分，并给出示例所需的结果。请参阅上面添加到dataframe/示例代码中的其他计数列。
merge(df, m)
##    student factor year count1 count2
## 1       S1      A    1      0      1
## 2       S1      C    2      0      1
## 3       S2      A    1      1      0
## 4       S2      B    1      1      0
## 5       S3      A    1      0      0
## 6       S4      A    1      0      0
## 7       S5      A    1      0      0
## 8       S6      B    1      0      0
## 9       S7      C    2      0      0
## 10      S8      D    2      0      0