R:合并两个data.table，同时过滤唯一ID:仅NA作为答案

library(data.table)

# 创建两个示例data.table
dt1 <- data.table(ID = c(1, 2, 3), Value1 = c("A", "B", "C"))
dt2 <- data.table(ID = c(2, 3, 4), Value2 = c("X", "Y", "Z"))

# 合并两个data.table
merged_dt <- merge(dt1, dt2, by = "ID")

# 输出合并结果
print(merged_dt)

   ID Value1 Value2
1:  2      B      X
2:  3      C      Y

library(data.table)

# 创建示例data.table
dt <- data.table(ID = c(1, 2, 2, 3, NA), Value = c("A", "B", "C", "D", "E"))

# 过滤唯一ID
filtered_dt <- unique(dt, by = "ID", fromLast = FALSE, incomparables = FALSE)

# 输出过滤结果
print(filtered_dt)

   ID Value
1:  1     A
2:  2     B
3:  3     D
4: NA     E