Question

我想按组计算tab $ date [i + 1]和tab $ date [i]之间的时差（以小时为单位）。这是我的代码：

.transcript {
    position: relative;
    width: 400px;
    height: 150px;
    background: #ffcc00;
    overflow-y: scroll;

    &:before {
        content: '';
        position: fixed;
        width: 400px; height: 20px;
        margin-top: 0; margin-left: 0;

        background: -webkit-linear-gradient(rgba(255, 255, 255, 1) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 0) 100%);
        background: -moz-linear-gradient(rgba(255, 255, 255, 1) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 0) 100%);
        background: -o-linear-gradient(rgba(255, 255, 255, 1) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 0) 100%);
        background: linear-gradient(rgba(255, 255, 255, 1) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 0) 100%);
    }

    &:after {
        content: '';
        position: fixed;
        top: 140px; left: 0;
        width: 400px; height: 20px;

        background: -webkit-linear-gradient(rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 1) 100%);
        background: -moz-linear-gradient(rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 1) 100%);
        background: -o-linear-gradient(rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 1) 100%);
        background: linear-gradient(rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0.7) 50%, rgba(255, 255, 255, 1) 100%);
    }
}

问题在于我获得了小时，分钟和秒：

setDT(tab)
system.time(tab <- tab[ , diffTime := c(0,diff(date, units="hours")), by="ID"])
tab$diffTime <- round(tab$diffTime)

日期是POSIXct数据。我怎么才能获得几个小时？

Answer 1

我们可以使用difftime并将units指定为'小时'。

library(data.table)
setDT(tab)[, DiffTime := c(0, round(difftime(date[-1L], date[-.N], 
                                 units='hours'))), by= ID]
tab
#   ID                date DiffTime
#1:  1 2012-03-05 01:00:36        0
#2:  1 2012-03-05 03:00:35        2
#3:  1 2012-03-05 05:01:05        2
#4:  2 2010-01-29 21:01:00        0 
#5:  2 2010-01-29 22:01:01        1
#6:  2 2010-01-29 23:01:12        1

数据

tab <- data.frame(ID= rep(1:2, each=3),
  date= as.POSIXct(c('2012-03-05 01:00:36', '2012-03-05 03:00:35', 
  '2012-03-05 05:01:05', '2010-01-29 21:01:00', '2010-01-29 22:01:01',
  '2010-01-29 23:01:12'), format='%Y-%m-%d %H:%M:%S'))

日期[i + 1]和日期[i]之间的时间差异

1 个答案:

数据