How to obtain named vector from single-column data frame?

Hello,

When you unlist, the dimension is dropped since the result is just one 
vector. Add drop = FALSE and that's it.


unlist(df[, "VarY", drop = FALSE])


Hope this helps,

Rui Barradas

?s 19:05 de 06/05/2022, Hooiveld, Guido escreveu:

Dear all,

I wrote a some code in which I 'convert' a data frame to a named vector using the function unlist(). This works very nicely for my use case, because each entry of the resulting vector is named after the column name of the data frame, with a number automatically appended. I am using these names for the subsequent part of my code.

However, I noticed that when I subset the data frame so it contains only a single column, the naming of the vector (as described above) doesn't occur anymore (i.e. names() = NULL). This breaks my downstream code. Any suggestion on how to still obtain a named vector from such single-column data frame?

Thanks,
Guido

df <- data.frame("VarX" = c("A",2,"D",2,1) ,

+  "VarY" = c(5,7,9,8,7) )

unlist(df) #nice!

VarX1 VarX2 VarX3 VarX4 VarX5 VarY1 VarY2 VarY3 VarY4 VarY5
   "A"   "2"   "D"   "2"   "1"   "5"   "7"   "9"   "8"   "7"

names(unlist(df))

  [1] "VarX1" "VarX2" "VarX3" "VarX4" "VarX5" "VarY1" "VarY2" "VarY3" "VarY4"
[10] "VarY5"

unlist(df[, "VarY"]) #where are the names now? Expected them to be "VarY1" ... "VarY5"

[1] 5 7 9 8 7

names(unlist(df[, "VarY"]))

NULL

______________________________________________
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.

Just use
names(unlist(df[, "VarY", drop=FALSE]))
# [1] "VarY1" "VarY2" "VarY3" "VarY4" "VarY5"

When you extract a single column from a data frame it converts it to a
vector by default.

David L Carlson



On Fri, May 6, 2022 at 1:05 PM Hooiveld, Guido <guido.hooiveld at wur.nl>
wrote:

Dear all, I wrote a some code in which I 'convert' a data frame to a named
vector using the function unlist(). This works very nicely for my use case,
because each entry of the resulting vector is named after the column name
of the data frame,
ZjQcmQRYFpfptBannerStart
This Message Is From an External Sender
This message came from outside your organization.

ZjQcmQRYFpfptBannerEnd

Dear all,

I wrote a some code in which I 'convert' a data frame to a named vector using the function unlist(). This works very nicely for my use case, because each entry of the resulting vector is named after the column name of the data frame, with a number automatically appended. I am using these names for the subsequent part of my code.

However, I noticed that when I subset the data frame so it contains only a single column, the naming of the vector (as described above) doesn't occur anymore (i.e. names() = NULL). This breaks my downstream code. Any suggestion on how to still obtain a named vector from such single-column data frame?

Thanks,
Guido

df <- data.frame("VarX" = c("A",2,"D",2,1) ,

+  "VarY" = c(5,7,9,8,7) )

unlist(df) #nice!

VarX1 VarX2 VarX3 VarX4 VarX5 VarY1 VarY2 VarY3 VarY4 VarY5
  "A"   "2"   "D"   "2"   "1"   "5"   "7"   "9"   "8"   "7"

names(unlist(df))

 [1] "VarX1" "VarX2" "VarX3" "VarX4" "VarX5" "VarY1" "VarY2" "VarY3" "VarY4"
[10] "VarY5"

unlist(df[, "VarY"]) #where are the names now? Expected them to be "VarY1" ... "VarY5"

[1] 5 7 9 8 7

names(unlist(df[, "VarY"]))

NULL

______________________________________________R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, seehttps://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXEBOEqSIog$
PLEASE do read the posting guide https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXECRkw_-4w$
and provide commented, minimal, self-contained, reproducible code.

Dear David and Rui,

Thanks a lot to both of you for your very fast answers; problem solved! :)

Regards,
Guido

From: David Carlson <dcarlson at tamu.edu>
Sent: 06 May 2022 20:26
To: Hooiveld, Guido <guido.hooiveld at wur.nl>
Cc: r-help at r-project.org
Subject: Re: [R] How to obtain named vector from single-column data frame?

Just use
names(unlist(df[, "VarY", drop=FALSE]))
# [1] "VarY1" "VarY2" "VarY3" "VarY4" "VarY5"

When you extract a single column from a data frame it converts it to a vector by default.

David L Carlson

Dear all, I wrote a some code in which I 'convert' a data frame to a named vector using the function unlist(). This works very nicely for my use case, because each entry of the resulting vector is named after the column name of the data frame,
ZjQcmQRYFpfptBannerStart
This Message Is From an External Sender
This message came from outside your organization.

ZjQcmQRYFpfptBannerEnd

Dear all,



I wrote a some code in which I 'convert' a data frame to a named vector using the function unlist(). This works very nicely for my use case, because each entry of the resulting vector is named after the column name of the data frame, with a number automatically appended. I am using these names for the subsequent part of my code.



However, I noticed that when I subset the data frame so it contains only a single column, the naming of the vector (as described above) doesn't occur anymore (i.e. names() = NULL). This breaks my downstream code. Any suggestion on how to still obtain a named vector from such single-column data frame?



Thanks,

Guido

df <- data.frame("VarX" = c("A",2,"D",2,1) ,

+  "VarY" = c(5,7,9,8,7) )

unlist(df) #nice!

VarX1 VarX2 VarX3 VarX4 VarX5 VarY1 VarY2 VarY3 VarY4 VarY5

  "A"   "2"   "D"   "2"   "1"   "5"   "7"   "9"   "8"   "7"

names(unlist(df))

[1] "VarX1" "VarX2" "VarX3" "VarX4" "VarX5" "VarY1" "VarY2" "VarY3" "VarY4"

[10] "VarY5"

unlist(df[, "VarY"]) #where are the names now? Expected them to be "VarY1" ... "VarY5"

[1] 5 7 9 8 7

names(unlist(df[, "VarY"]))

NULL

______________________________________________

R-help at r-project.org<mailto:R-help at r-project.org> mailing list -- To UNSUBSCRIBE and more, see

https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-help__;!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXEBOEqSIog$<https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Furldefense.com%2Fv3%2F__https%3A%2F%2Fstat.ethz.ch%2Fmailman%2Flistinfo%2Fr-help__%3B!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXEBOEqSIog%24&data=05%7C01%7Cguido.hooiveld%40wur.nl%7Cbdd102be7b9042ccfec508da2f8df4c0%7C27d137e5761f4dc1af88d26430abb18f%7C0%7C0%7C637874584008711589%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=UGXlmkwuoBkGb%2F7dLZ0%2F3iFXJ9rtabtRB8%2FZ1sbMe8g%3D&reserved=0>

PLEASE do read the posting guide https://urldefense.com/v3/__http://www.R-project.org/posting-guide.html__;!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXECRkw_-4w$<https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Furldefense.com%2Fv3%2F__http%3A%2F%2Fwww.R-project.org%2Fposting-guide.html__%3B!!KwNVnqRv!EUndg3P-mraBuPMXbhvgZkIok13frVGjcD2ebHWlTHVrETkmNqEfYu0YPT6BEisdkhcijOfxsGlfsGoPXECRkw_-4w%24&data=05%7C01%7Cguido.hooiveld%40wur.nl%7Cbdd102be7b9042ccfec508da2f8df4c0%7C27d137e5761f4dc1af88d26430abb18f%7C0%7C0%7C637874584008711589%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=okqIQIFy6e1vHNTqezf8cDO2tmt%2BuZnqCe98CUnGknQ%3D&reserved=0>

and provide commented, minimal, self-contained, reproducible code.