计算变量 R 上的变量 [英] Count variable on a Variable R

问题描述

Tid <- c(1,1,2,2,2,3,4,4)
Uid <- c(10,10,11,11,12,13,10,14)

Data <- data.frame(Tid,Uid)

我想知道每个 Tid 上出现了多少个不同的 Uid.我的结果应该是这样的.

I would like to know how many different Uid appear on every Tid. My Results should look something like this.

Tid, freqUid 
1, 1
2, 2
3, 1
4, 2

我尝试对它使用计数，但在将它用于不止一个变量时遇到了一些问题.

I tried to use count on it but had some issues to use it on more then just one variable.

推荐答案

with base R

With base R

as.data.frame(table(unique(Data)$Tid))
#   Var1 Freq
# 1    1    1
# 2    2    2
# 3    3    1
# 4    4    2

或者(虽然列名的信息量较少)

Or (though the column name is less informative)

aggregate(Uid ~ Tid, unique(Data), length)
#   Tid Uid
# 1   1   1
# 2   2   2
# 3   3   1
# 4   4   2

<小时>

这里的基本思想是只对Tid/Uid的唯一组合进行操作，然后统计不同的Tid实例

---

The basic idea here is to only operate on the unique combinations of Tid/Uid and then count the different Tid instances

根据@nicolas 评论，我们也可以在此处添加 tapply 作为可能的解决方案

per @nicolas comment, we can add tapply too here as a possible solution

as.data.frame.table(tapply(Data$Uid, Data$Tid, function(x) length(unique(x))))
#   Var1 Freq
# 1    1    1
# 2    2    2
# 3    3    1
# 4    4    2

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