如何在R语言中按Product分组统计唯一Patient_ID的数量？

可复现数据集 #

test_data <- data.frame(Product=c("A","A","A","A","D","D","D","E","E","F","G"),
                        Patient_ID=c("1","1","1","3","3","4","5","5","6","7","8"))

方法1：基础R实现 #

通过aggregate函数分组计算唯一患者数：

result_base <- aggregate(Patient_ID ~ Product, data = test_data, 
                         FUN = function(x) length(unique(x)))
colnames(result_base)[2] <- "Freq"
# 输出结果
result_base

方法2：dplyr包实现（tidyverse风格） #

先加载dplyr，通过去重后计数的方式实现：

library(dplyr)

result_dplyr <- test_data %>%
  distinct(Product, Patient_ID) %>%  # 保留唯一的产品-患者组合
  count(Product, name = "Freq")     # 按产品统计数量

# 输出结果
result_dplyr

最终输出结果 #

两种方法均会得到如下数据集：

Product Freq
1       A    2
2       D    3
3       E    2
4       F    1
5       G    1

内容的提问来源于stack exchange，提问作者sabc04