Subset / filter rows of a data.frame by non-standard formatted date-CodePudding

I have a hourly data.frame Data with a $date column from years 2015 to 2021. The dates are in "%d%m%Y HH:MM" format.

I need to remove specific rows with a certain date, e.g. remove all rows with date "01/09/2021".

I tried this:

Data <- Data[as.Date(format(Data$date, "%d%m%Y")) != 01/09/2021, ]

but this didn´t work. What's the correct way to do it? Thanks in advance for your help.

CodePudding user response：

The date-time conversion codes are listed in ?strptime.

as.Date returns a string of type "2021-09-01" and class Date (see ?Dates for details), so this would be the correct logic:

Data <- data.frame(id = 1:2, date = c("01012021 00:00","01092021 00:00"))
Data
#>   id           date
#> 1  1 01012021 00:00
#> 2  2 01092021 00:00

Data[as.Date(Data$date, format = "%d%m%Y") != "2021-09-01", ]
#>   id           date
#> 1  1 01012021 00:00

Note that strings such as "01/09/2021" or "2021-09-01" have to be quoted in R.

^{Created on 2021-09-21 by the reprex package (v2.0.1)}

Does this help?

CodePudding user response：

You can use regex approach to remove rows that start with '01092021'.

Using data from @scrameri

result <- subset(Data, !grepl('^01092021', date))
result

#  id           date
#1  1 01012021 00:00