[R] How to modify rows matching patter on multiple columns of dataframe?

[Luigi Marongiu]

Thank you! both hacks worked as needed!

On Thu, Aug 12, 2021 at 6:59 PM Rui Barradas <ruipbarradas using sapo.pt> wrote:
>
> Hello,
>
> And another way, with which(., arr.ind = TRUE).
> In two steps, to make it clearer.
>
>
> i <- which(df[grep("var[123]", names(df))] == "a", arr.ind = TRUE)
> df[i] <- "z"
>
> df
> #  var1 var2 var3 var4  var5
> #1    z    A    z    1 light
> #2    b    B    b    4 light
> #3    c    C    c    9 heavy
> #4    z    D    z   16 heavy
> #5    b    E    b   25 heavy
> #6    c    F    c   36 light
> #7    d    G    d   49 heavy
>
>
> Hope this helps,
>
> Rui Barradas
>
>
> Às 13:37 de 12/08/21, Luigi Marongiu escreveu:
> > Helo
> > I have a dataframe whose names are similar and I would like to change
> > the rows containing given values simultaneously.
> > I can select the columns using library(dplyr) but I can't modify the data:
> > ```
> > library(dplyr)
> >> df <- data.frame(var1 = c(letters[1:3], letters[1:4]),
> > +                 var2 = c(LETTERS[1:7]),
> > +                 var3 = c(letters[1:3], letters[1:4]),
> > +                 var4 = (1:7)^2,
> > +                 var5 = c("light", "light", "heavy", "heavy", "heavy",
> > +                          "light", "heavy"),
> > +                 stringsAsFactors = FALSE); df
> >    var1 var2 var3 var4  var5
> > 1    a    A    a    1 light
> > 2    b    B    b    4 light
> > 3    c    C    c    9 heavy
> > 4    a    D    a   16 heavy
> > 5    b    E    b   25 heavy
> > 6    c    F    c   36 light
> > 7    d    G    d   49 heavy
> >> select(df, matches("var[123]"))
> >    var1 var2 var3
> > 1    a    A    a
> > 2    b    B    b
> > 3    c    C    c
> > 4    a    D    a
> > 5    b    E    b
> > 6    c    F    c
> > 7    d    G    d
> >> df[[select(df, matches("var[123]")) == "a"]] <- "z"
> > Error in `[[<-`(`*tmp*`, i, value = value) :
> >    recursive indexing failed at level 2
> >> df[[select(df, contains("var1")) == "a"]] <- "z"
> > Error in `[[<-`(`*tmp*`, i, value = value) :
> >    recursive indexing failed at level 2
> > ```
> > If I sue which, I get a wrong substitution :
> > ```
> >> df[which(select(df, matches("var[123]")) == "a"), ] <- "z"; df
> >     var1 var2 var3 var4  var5
> > 1     z    z    z    z     z
> > 2     b    B    b    4 light
> > 3     c    C    c    9 heavy
> > 4     z    z    z    z     z
> > 5     b    E    b   25 heavy
> > 6     c    F    c   36 light
> > 7     d    G    d   49 heavy
> > 8  <NA> <NA> <NA> <NA>  <NA>
> > 9  <NA> <NA> <NA> <NA>  <NA>
> > 10 <NA> <NA> <NA> <NA>  <NA>
> > 11 <NA> <NA> <NA> <NA>  <NA>
> > 12 <NA> <NA> <NA> <NA>  <NA>
> > 13 <NA> <NA> <NA> <NA>  <NA>
> > 14 <NA> <NA> <NA> <NA>  <NA>
> > 15    z    z    z    z     z
> > 16 <NA> <NA> <NA> <NA>  <NA>
> > 17 <NA> <NA> <NA> <NA>  <NA>
> > 18    z    z    z    z     z
> > ```
> >
> > what is the correct syntax?
> > Thank you
> >



-- 
Best regards,
Luigi