FOR循环以计算R中日期的差异 [英] FOR loop to calculate difference on dates in R

问题描述

我正在尝试计算以天为单位的数据帧中两个日期之间的差异，并将其保存在同一数据帧的称为延迟的另一列中.这是我的代码，但是不起作用:

I am trying to calculate the difference between two dates in a data frame in days and save it in another column of the same data frame called lag. This is my code but it is not working:

Daily_Streamflow$Date
Daily_Streamflow$lag[1] <- 0
j <- 2
for (j in length(Daily_Streamflow$Date)) {
 Daily_Streamflow$lag[j] <-  as.numeric(difftime(Daily_Streamflow$Date[j],Daily_Streamflow$Date[j-1], unit=c("days")))
 j <- j + 1
}

这是我的数据框的外观:

This is how my data frame looks:

当我将第一天的差值设置为 Daily_Streamflow $ lag [1] 等于0时，所有剩余值都设置为0.如果我将此值保留为空，则该列的所有值设置为 NA .看起来，虽然j值增加并且循环运行，但是代码将第一个滞后值赋给了所有列，忽略了for内部的函数.

When I set the difference for the first day Daily_Streamflow$lag[1] equal to 0 all the remaining values are set to 0. If I keep this value empty, all the values of the column are set to NA. It seems that the code put the value of the first lag to all the column, omitting the function inside the for, though the j value increases and the loop runs.

推荐答案

由于您没有为我们提供数据，因此您必须自己进行测试:

Since you didn't provide data for us, you have to test this by yourself:

Daily_Streamflow$Date
Daily_Streamflow$lag[1] <- 0
for (j in 2:length(Daily_Streamflow$Date)) { # add 2: to create a sequence
  Daily_Streamflow$lag[j] <-  as.numeric(difftime(Daily_Streamflow$Date[j],Daily_Streamflow$Date[j-1], units=c("days")), units = "days") # change 'unit' to 'units' and add 'units' attribute to the 'as.numeric' function as well
  j <- j + 1
}

这篇关于FOR循环以计算R中日期的差异的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！