如何使用 rbind 将数据表与 POSIXct 和 Date 列类合并？答案

【问题标题】：How to use rbind to merge data tables with POSIXct and Date column classes?如何使用 rbind 将数据表与 POSIXct 和 Date 列类合并？
【发布时间】：2015-03-31 13:02:11
【问题描述】：

我想合并两个数据表，但其中一个具有ddate 列和POSIXct 类，另一个具有ddate 列和Date 类。

我希望结果数据表具有POSIXct 类，但实际结果取决于传递给rbind 的参数序列：

zz1 <- "or,d,ddate,rdate,changes,class,price,fdate,company,number,minutes,added,source
VA1,VA2,2014-05-24,,0,0,2124,2014-05-22 15:50:16,,,,2014-05-22 12:20:03,ss
VA1,VA2,2014-05-26,,0,0,2124,2014-05-22 15:03:44,,,,2014-05-22 12:20:03,s1
VA1,VA2,2014-06-05,,0,0,2124,2014-05-22 15:48:24,,,,2014-05-22 12:20:03,s1
VA1,VA2,2014-06-09,,0,0,2124,2014-05-22 15:37:35,,,,2014-05-22 12:20:03,s2
VA1,VA2,2014-06-16,,0,0,2124,2014-05-22 14:17:33,,,,2014-05-22 12:20:03,ss"

zz2 <- "or,d,ddate,rdate,changes,class,price,fdate,company,number,minutes,added,source
VA3,VA4,2014-05-24 12:23:00,,0,0,2124,2014-05-22 15:50:16,,,,2014-05-22 12:20:03,ss
VA1,VA2,2014-05-26 14:00:01,,0,0,2124,2014-05-22 15:03:44,,,,2014-05-22 12:20:03,s1
VA5,VA6,2014-06-05 18:00:04,,0,0,2124,2014-05-22 15:48:24,,,,2014-05-22 12:20:03,s1
VA7,VA8,2014-06-09 18:00:07,,0,0,2124,2014-05-22 15:37:35,,,,2014-05-22 12:20:03,s2
VA9,VA0,2014-06-16 19:00:20,,0,0,2124,2014-05-22 14:17:33,,,,2014-05-22 12:20:03,ss"

columnClasses <- c("factor", "factor", "Date", "factor", "integer", "factor", "integer", "factor", "factor", "factor", "integer", "factor", "factor")
dt1 <- read.table(text=zz1, header = TRUE, sep = ",", comment.char = "", quote = "", na.strings = c(""), colClasses = columnClasses)

columnClasses <- c("factor", "factor", "POSIXct", "factor", "integer", "factor", "integer", "factor", "factor", "factor", "integer", "factor", "factor")
dt2 <- read.table(text=zz2, header = TRUE, sep = ",", comment.char = "", quote = "", na.strings = c(""), colClasses = columnClasses)

dt <- rbind(dt1, dt2)
class(dt$ddate) # [1] "Date"

dt <- rbind(dt2, dt1)
class(dt$ddate) # [1] "POSIXct" "POSIXt"

我应该怎么做才能始终拥有POSIXct？因为当我从下面的 CSV 文件中获取数据时，我无法控制顺序：

tables <- lapply(files, readCSVFile)
dt <- rbindlist(tables, fill = TRUE)

【问题讨论】：

标签： r data.table

【解决方案1】：

我认为您可以在使用read.csv 加载时处理每个文件，以便将ddate 变量转换为POSIXct。然后可以更好地控制合并。这可以通过创建供lapply 使用的您自己的函数来完成。

示例

ddate.convert = function(x){tmp <- readcsv(x); tmp$ddate <- as.POSIXct(tmp$ddate); tmp}
tables <- lapply(files, FUN=ddate.convert)
dt <- rbindlist(tables, fill = TRUE)

【讨论】：