R help - Oct 2022 - Unexpected result for df column $ subset with non-existent name

Hi All,

Just noticed that R returns results for non-existent name if you have
another variable with the same beginning when you subset with $.
See the code below:
name_0 <- "ID"
name_1 <- "name"
name_2 <- "name1"

v0 <- 1:200
v1 <- c(rep(0,100), rep(1,100))
v2 <- c(rep(0,50), rep(1,150))

df <- as.data.frame(cbind(v0, v1, v2))
colnames(df) <- c(name_0, name_1, name_2)

df_1 <- df[, c(name_0, name_1)]
df_2 <- df[, c(name_0, name_2)]

table(df$name)
table(df_1$name)
table(df_2$name)
colnames(df_2)[2] <- "name10"
table(df_2$name)
colnames(df_2)[2] <- "name_any"
table(df_2$name)
table(df_2[,"name"])

The last row produces an error as intended.
Any ideas?

Win 10
R version 4.2.1 (2022-06-23 ucrt) -- "Funny-Looking Kid"

Regards,
Sergiy

	[[alternative HTML version deleted]]

Does this explain it: (from ?Extract)


name
A literal character string or a name (possibly backtick quoted). For
extraction, this is normally (see under ?Environments?) **partially
matched** to the names of the object.

-- Bert

On Fri, Oct 28, 2022 at 6:53 AM Sergei Ko <sggp.sergei at gmail.com>
wrote:
>
> Hi All,
>
> Just noticed that R returns results for non-existent name if you have
> another variable with the same beginning when you subset with $.
> See the code below:
> name_0 <- "ID"
> name_1 <- "name"
> name_2 <- "name1"
>
> v0 <- 1:200
> v1 <- c(rep(0,100), rep(1,100))
> v2 <- c(rep(0,50), rep(1,150))
>
> df <- as.data.frame(cbind(v0, v1, v2))
> colnames(df) <- c(name_0, name_1, name_2)
>
> df_1 <- df[, c(name_0, name_1)]
> df_2 <- df[, c(name_0, name_2)]
>
> table(df$name)
> table(df_1$name)
> table(df_2$name)
> colnames(df_2)[2] <- "name10"
> table(df_2$name)
> colnames(df_2)[2] <- "name_any"
> table(df_2$name)
> table(df_2[,"name"])
>
> The last row produces an error as intended.
> Any ideas?
>
> Win 10
> R version 4.2.1 (2022-06-23 ucrt) -- "Funny-Looking Kid"
>
> Regards,
> Sergiy
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.

?s 14:52 de 28/10/2022, Sergei Ko escreveu:
> Hi All,
> 
> Just noticed that R returns results for non-existent name if you have
> another variable with the same beginning when you subset with $.
> See the code below:
> name_0 <- "ID"
> name_1 <- "name"
> name_2 <- "name1"
> 
> v0 <- 1:200
> v1 <- c(rep(0,100), rep(1,100))
> v2 <- c(rep(0,50), rep(1,150))
> 
> df <- as.data.frame(cbind(v0, v1, v2))
> colnames(df) <- c(name_0, name_1, name_2)
> 
> df_1 <- df[, c(name_0, name_1)]
> df_2 <- df[, c(name_0, name_2)]
> 
> table(df$name)
> table(df_1$name)
> table(df_2$name)
> colnames(df_2)[2] <- "name10"
> table(df_2$name)
> colnames(df_2)[2] <- "name_any"
> table(df_2$name)
> table(df_2[,"name"])
> 
> The last row produces an error as intended.
> Any ideas?
> 
> Win 10
> R version 4.2.1 (2022-06-23 ucrt) -- "Funny-Looking Kid"
> 
> Regards,
> Sergiy
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.
Hello,

This behavior, partial matching of column or list members names when 
extracting with `$` is practically a FAQ.
See the latest R-Help thread on it after the release of R 4.0


https://stat.ethz.ch/pipermail/r-help/2020-May/467143.html


Hope this helps,

Rui Barradas