在dataframe中选择列时出错

这可能是一个非常简单的问题，但我仍然无法找出我错在哪里

我必须遵循数据帧

 Data3 <- structure(list(P1 = c("DAVID SKOCH", "VIKTOR TROICKI", "PETER LUCZAK", 
                  "SIMON STADLER", "PHILIPP PETZSCHNER", "JAMIE MURRAY", "MICHAL MERTINAK", 
                  "IGOR KUNITSYN", "DANIEL MUNOZ DE LA NAVA", "ALEXANDRE SIDORENKO"), 
           P2 = c("LOVRO ZOVKO", "DMITRI SITAK", "MARTIN VASSALLO ARGUELLO", 
                  "SEBASTIEN DE CHAUNAC", "N.SRIRAM BALAJI", "JAROSLAV LEVINSKY", 
                  "STEPHEN AMRITRAJ", "WESLEY MOODIE", "ANDREY GOLUBEV", "NICOLAS TOURTE"), 
           Date = structure(c(1167618386.44068, 1167619381.13208, 1167622892.30769, 
                                 1167626322.58065, 1167627172.88136, 1167629162.26415, 1167635959.32203, 
                                 1167636184.61538, 1167638943.39623, 1167643045.16129), tzone = "UTC", class = c("POSIXct","POSIXt")), 
           Factor = c(0.82, 1.28, 1.37, 1.37, 1.28, 1.28, 1.46, 0.73, 1.82, 1.55), Weight = c(1.1, 1.1, 1.1, 1.1, 1.1, 1.1, 1.1, 1.1, 1.1, 1.1)), 
      .Names = c("P1", "P2", "Date", "Factor", "Weight"), class = c("data.table", "data.frame"), row.names = c(NA, -10L))

不幸的是，结果如下：

[1] "Weight" "Date"   "Factor"

而不是选择具有指定列的数据帧

---

有什么提示吗？

我们需要使用

with=FALSE

，因为它是一个

数据表

Data3[,c("Weight","Date","Factor"), with = FALSE]

或使用数据。表格语言：data3[，（重量、日期、系数）]？
Data3[,c("Weight","Date","Factor"), with = FALSE]