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François Michonneau <[log in to unmask]>
3:43 PM (4 minutes ago)
to UF
Hi Nihal

  Here is a possible solution

```
library(tidyverse)
library(readxl)

dt <- read_excel("example_for_R_listerv.xlsx", skip = 1) %>%
  mutate(date = format(time, "%Y-%m-%d"))
```

If your dates are already properly formatted, you don't have to use regular
expressions. The functions that read data in the tidyverse detect
automatically that it's a date and parse them as such. Once your data is in
the date format, you can use the "format" function to extract the year
(%Y), month (%m) and day (%d) in a new column here named "date". However,
depending on what you are trying to accomplish with your data you may not
have to do that. For instance, you can filter for a time period directly on
your initial column without having to extract the exact day.

Also note that I put "skip = 1" and the column headers are actually not in
your first row of the spreadsheet (which might be why the "time" column was
not recognized in the code example you sent).

  I hope this helps.

  Best
  -- François


On Fri, Jul 27, 2018 at 3:31 PM El Rouby,Nihal M <[log in to unmask]>
wrote:

> Dear All-
>
>
>
> Trying to extract dates from a variable in a data frame and then make a
> new column with these dates. I’m using regular expression along str_extract
> command from package stringr.
>
>
>
> I’m getting the error  “Error in geno_time$time : $ operator is invalid
> for atomic vectors” when I used this command below on my dataframe.
>
>
>
> geno_time<-str_extract(geno_time$time,"[0-9]+\\/[0-9]+\\/[0-9]+[:blank:]?")
>
>
>
> I’m attaching example of my data and what I want to accomplish.
>
>
>
> I appreciate your input and have a great weekend.
>
>
>
> Best,
>
> Nihal
> This list strives to be beginner friendly. However, we still ask that you
> PLEASE do read the posting guide
> https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.org_posting-2Dguide.html&d=DwIFaQ&c=pZJPUDQ3SB9JplYbifm4nt2lEVG5pWx2KikqINpWlZM&r=QWxQId63qB2iSP1ggUL7kQsdfEWUTu6qCGEw8Xuo91A&m=1gxtMVlwUy1KieIIAZ2D3z9XGGtD9blndoZwqdPs73o&s=YNlMgsazQduCXywYwompcIbfwGIRLF4Rtq3BQ8cVz28&e= and provide commented,
> minimal, self-contained, reproducible code.
>

This list strives to be beginner friendly.  However, we still ask that you
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.