如何在R中跨两个数据帧编写条件值？

# 假设有两个数据帧df1和df2
df1 <- data.frame(id = 1:5, value1 = c(10, 20, 30, 40, 50))
df2 <- data.frame(id = 1:5, value2 = c(15, 25, 35, 45, 55))

# 使用merge()函数根据id列合并数据帧
merged_df <- merge(df1, df2, by = "id")

# 应用条件逻辑
merged_df$result <- ifelse(merged_df$value1 > merged_df$value2, "value1大", "value2大")

print(merged_df)

# 安装并加载dplyr包
install.packages("dplyr")
library(dplyr)

# 使用left_join()根据id列连接数据帧
joined_df <- left_join(df1, df2, by = "id")

# 应用条件逻辑
joined_df$result <- ifelse(joined_df$value1 > joined_df$value2, "value1大", "value2大")

print(joined_df)

# 安装并加载data.table包
install.packages("data.table")
library(data.table)

# 将数据帧转换为data.table
setDT(df1)
setDT(df2)

# 使用merge()函数根据id列合并数据帧
merged_dt <- merge(df1, df2, by = "id")

# 应用条件逻辑
merged_dt$result <- ifelse(merged_dt$value1 > merged_dt$value2, "value1大", "value2大")

print(merged_dt)