[R] Apply gsub to dataframe to modify row values

Jim Lemon
Mon, 09 Aug 2021 11:32:50 -0000

Hi Luigi,
You want to get rid of certain strings in the "VAL" column. You are
assigning to:

df[df$VAL]
Error in `[.data.frame`(df, df$VAL) : undefined columns selected

when I think you should be assigning to:

df$VAL

What do you want to remove other than "[V|v]alue is" ?

JIim

On Mon, Aug 9, 2021 at 8:50 PM Luigi Marongiu <marongiu.luigi at
gmail.com> wrote:
>
> Sorry, silly question, gsub works already with regex. But still, if I
> add `[[:blank:]]` still I don't get rid of all instances. And I am
> keeping obtaining extra columns
> ```
> > df[df$VAL] = gsub("[[:blank:]Value is]", "",
df$VAL, ignore.case=TRUE)
> > df[df$VAL] = gsub("[[:blank:]Value is]", "",
df$VAL, ignore.case=TRUE);df
>   VAR           VAL value is blue Value is red empty
> 1   1 value is blue             b            b     b
> 2   2  Value is red            rd           rd    rd
> 3   3         empty          mpty         mpty  mpty
> ```
>
> On Mon, Aug 9, 2021 at 12:40 PM Luigi Marongiu <marongiu.luigi at
gmail.com> wrote:
> >
> > Thank you, that is much appreciated. But on the real data, the
> > substitution works only on few instances. Is there a way to introduce
> > regex into this?
> > Cheers
> > Luigi
> >
> > On Mon, Aug 9, 2021 at 11:01 AM Jim Lemon <drjimlemon at
gmail.com> wrote:
> > >
> > > Hi Luigi,
> > > Ah, now I see:
> > >
> > >  df$VAL<-gsub("Value
is","",df$VAL,ignore.case=TRUE)
> > > df
> > >  VAR   VAL
> > > 1   1  blue
> > > 2   2   red
> > > 3   3 empty
> > >
> > > Jim
> > >
> > > On Mon, Aug 9, 2021 at 6:43 PM Luigi Marongiu <marongiu.luigi
at gmail.com> wrote:
> > > >
> > > > Hello,
> > > > I have a dataframe where I would like to change the string
of certain
> > > > rows, essentially I am looking to remove some useless text
from the
> > > > variables.
> > > > I tried with:
> > > > ```
> > > > > df = data.frame(VAR = 1:3, VAL = c("value is
blue", "Value is red", "empty"))
> > > > > df[df$VAL] = gsub("value is ", "",
df$VAL, ignore.case = TRUE, perl = FALSE)
> > > > > df
> > > >   VAR           VAL value is blue Value is red empty
> > > > 1   1 value is blue          blue         blue  blue
> > > > 2   2  Value is red           red          red   red
> > > > 3   3         empty         empty        empty empty
> > > > ```
> > > > which is of course wrong because I was expecting
> > > > ```
> > > >   VAR           VAL
> > > > 1   1             blue
> > > > 2   2             red
> > > > 3   3            empty
> > > > ```
> > > > What is the correct syntax in these cases?
> > > > Thank you
> > > >
> > > > ______________________________________________
> > > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and
more, see
> > > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> > > > and provide commented, minimal, self-contained, reproducible
code.
> >
> >
> >
> > --
> > Best regards,
> > Luigi
>
>
>
> --
> Best regards,
> Luigi