Time format lagging issue

Try following this example:

mydf <- data.frame(t1=c('201112312230', '201112312330'))
tmp1 <- as.POSIXct(mydf$t1, format='%Y%m%d%H%M')
tmp2 <- tmp1 - 30*60
mydf$t2 <- format(tmp2, '%Y%m%d%H%M')

It can be made into a single line, but I used intermediate variables tmp1
and tmp2 so that it would be easier to follow.

Base R is more than adequate for this task.

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On 8/31/16, 9:07 AM, "R-help on behalf of Bhaskar Mitra"
<r-help-bounces at r-project.org on behalf of bhaskar.kolkata at gmail.com>
wrote:

Hello Everyone,

I am trying a shift the time series in a dataframe (df) by 30 minutes . My
current format looks something like this :



*df$$Time 1*


*201112312230*

*201112312300*

*201112312330*



*I am trying to add an additional column of time (df$Time 2) next to  Time
1 by lagging it by ? 30minutes. Something like this :*


*df$Time1                   **df$$Time2*


*201112312230          **201112312200*

*201112312300          **201112312230*

*201112312330          **201112312300*

*201112312330          *





*Based on some of the suggestions available, I have tried this option *



*require(zoo)*

*df1$Time2  <- lag(df1$Time1, -1, na.pad = TRUE)*

*View(df1)*



*This does not however give me the desired result. I would appreciate any
suggestions/advice in this regard.*


*Thanks,*

*Bhaskar*

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