R help - Aug 2021 - substitute column data frame based on name stored in variable in r

Thanks for providing a reproducible example!

On Mon, 9 Aug 2021 15:33:53 +0200
Luigi Marongiu <marongiu.luigi at gmail.com> wrote:
> df[df[['vect[2]']] == 2, 'vect[2]'] <- "No"
Please don't quote R expressions that you want to evaluate.
'vect[2]'
is just a string, like 'hello world' or 'I want to create a new
column
named "vect[2]" instead of accessing the second one'.
> Error in `[<-.data.frame`(`*tmp*`, df[[vect[2]]] == 2, vect[2], value
> = "No") : missing values are not allowed in subscripted
assignments
> of data frames
Since df[[2]] containts NAs, comparisons with it also contain NAs. While
it's possible to subset data.frames with NAs (the rows corresponding to
the NAs are returned filled with NAs of corresponding types),
assignment to undefined rows is not allowed. A simple way to remove the
NAs and only leave the cases where df[[vect[2]]] == 2 is TRUE would be
to use which(). Compare:

df[df[[vect[2]]] == 2,]
df[which(df[[vect[2]]] == 2),]

-- 
Best regards,
Ivan

Thank you! it worked fine! The only pitfall is that `NA` became
`<NA>`. This is essentially the same thing anyway...

On Mon, Aug 9, 2021 at 5:18 PM Ivan Krylov <krylov.r00t at gmail.com>
wrote:
>
> Thanks for providing a reproducible example!
>
> On Mon, 9 Aug 2021 15:33:53 +0200
> Luigi Marongiu <marongiu.luigi at gmail.com> wrote:
>
> > df[df[['vect[2]']] == 2, 'vect[2]'] <-
"No"
>
> Please don't quote R expressions that you want to evaluate.
'vect[2]'
> is just a string, like 'hello world' or 'I want to create a new
column
> named "vect[2]" instead of accessing the second one'.
>
> > Error in `[<-.data.frame`(`*tmp*`, df[[vect[2]]] == 2, vect[2],
value
> > = "No") : missing values are not allowed in subscripted
assignments
> > of data frames
>
> Since df[[2]] containts NAs, comparisons with it also contain NAs. While
> it's possible to subset data.frames with NAs (the rows corresponding to
> the NAs are returned filled with NAs of corresponding types),
> assignment to undefined rows is not allowed. A simple way to remove the
> NAs and only leave the cases where df[[vect[2]]] == 2 is TRUE would be
> to use which(). Compare:
>
> df[df[[vect[2]]] == 2,]
> df[which(df[[vect[2]]] == 2),]
>
> --
> Best regards,
> Ivan


-- 
Best regards,
Luigi