[R] substract start from the end of the vector

[Steve Lianoglou]

Hi,

On Fri, Apr 23, 2010 at 11:57 AM, arnaud Gaboury
<arnaud.gaboury at gmail.com> wrote:
> Dear group,
>
> Here is my df :
>
> df <-
>
> structure(list(DESCRIPTION = c("PRM HGH GD ALUMINIUM USD 09/07/10 ",
>
> "PRM HGH GD ALUMINIUM USD 09/07/10 ", "PRIMARY NICKEL USD 04/06/10 "
>
> ), CREATED.DATE = structure(c(18361, 18361, 18325), class = "Date"),
>
>    QUANITY = c(-1L, 1L, 1L), CLOSING.PRICE = c("2,415.90", "2,415.90",
>
>    "25,755.71")), .Names = c("DESCRIPTION", "CREATED.DATE",
>
> "QUANITY", "CLOSING.PRICE"), row.names = c(NA, 3L), class = "data.frame")
>
>>
>
>> df
>
>                         DESCRIPTION                   CREATED.DATE
> QUANITY          CLOSING.PRICE
>
> 1 PRM HGH GD ALUMINIUM USD 09/07/10    2020-04-09               -1
> 2,415.90
>
> 2 PRM HGH GD ALUMINIUM USD 09/07/10    2020-04-09                1
> 2,415.90
>
> 3              PRIMARY NICKEL USD 04/06/10    2020-03-04                1
> 25,755.71
>
> In the DESCRIPTION column, I want to get rid of the date (09/07/10 .). I
> know the function substr(x, start, stop), but in my case, I need to indicate
> I want to start from the end of the vector, and I have no idea how to pass
> this argument.
>
> TY for any help

How about using a regular expression:

R> gsub(" *(\\d+/\\d+/\\d+)$", "", "HGH GD ALUMINIUM USD 09/07/10", perl=TRUE)
[1] "HGH GD ALUMINIUM USD"

And to replace your DESCRIPTION clolumn

R> df$DESCRIPTION <- gsub(" *(\\d+/\\d+/\\d+) *$", "", df$DESCRIPTION)
R> df
               DESCRIPTION CREATED.DATE QUANITY CLOSING.PRICE
1 PRM HGH GD ALUMINIUM USD   2020-04-09      -1      2,415.90
2 PRM HGH GD ALUMINIUM USD   2020-04-09       1      2,415.90
3       PRIMARY NICKEL USD   2020-03-04       1     25,755.71

I'm also removing leading/trailing spaces around your date to strip
out any trailing whitespace.

HTH,
-steve

-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
 | Memorial Sloan-Kettering Cancer Center
 | Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact