Question

我正在尝试汇总我的数据，以说明老师安排的课程数量。

基本上我的数据如下：

Id | Subject
123| algebra
123| geometry
123| algebra II
456| calc
456| calc
789| geometry
789| geometry
789| calc

and I need it to look like this:

Id | Subject count
123| 3
456| 1
789| 2

I have no idea where to start because I don't want it to simply count the number of courses they teach, I want the DIFFERENT courses. Please help!

Answer 1

我们可以按'Id'分组，并在n_distinct中用summarise获得不同的'Subject'计数

library(dplyr)
df1 %>%
  group_by(Id) %>%
  summarise(Subject_Count = n_distinct(Subject))
# A tibble: 3 x 2
#     Id Subject_Count
#  <int>         <int>
#1   123             3
#2   456             1
#3   789             2

或者使用data.table转换为{Id}分组的data.table（setDT(df1)），并用uniqueN来获得不同的计数

library(data.table)
setDT(df1)[,.(Subject_Count = uniqueN(Subject)), by = Id]

数据

df1 <- structure(list(Id = c(123L, 123L, 123L, 456L, 456L, 789L, 789L, 
789L), Subject = c("algebra", "geometry", "algebra II", "calc", 
"calc", "geometry", "geometry", "calc")), class = "data.frame",
row.names = c(NA, 
-8L))

通过变化计数汇总数据？

1 个答案:

数据