使用R将时间格式转换为数字

In most cases,we convert numeric time to posixct format using R. However, sometimes, we want to compare which time point is earlier, then we would prefer the numeric time format. Thus, it's quite practical question to convert time format to numeric. For example,I have the data format like "2001-03-13 10:31:00",In most cases,we convert numeric time to posixc