How to rename a single column in a data.frame?

Question

I know if I have a data frame with more than 1 column, then I can use

colnames(x) <- c("col1","col2")

to rename the columns. How to do this if it's just one column? Meaning a vector or data frame with only one column.

Example:

trSamp <- data.frame(sample(trainer$index, 10000))
head(trSamp )
#   sample.trainer.index..10000.
# 1                      5907862
# 2                      2181266
# 3                      7368504
# 4                      1949790
# 5                      3475174
# 6                      6062879

ncol(trSamp)
# [1] 1
class(trSamp)
# [1] "data.frame"
class(trSamp[1])
# [1] "data.frame"
class(trSamp[,1])
# [1] "numeric"
colnames(trSamp)[2] <- "newname2"
# Error in names(x) <- value : 
#   'names' attribute [2] must be the same length as the vector [1]

@aix's solution will work for a 1-column data.frame. You're probably being confused by the `drop=TRUE` default argument to `[`, which causes a "1-column" object to be converted to a vector... and vectors don't have `colnames`. An example of what you tried would be very helpful. — Joshua Ulrich, Sep 23 '11 at 16:31

score 703 · Answer 1 · edited Dec 28 '16 at 23:27

703

This is a generalized way in which you do not have to remember the exact location of the variable:

# df = dataframe
# old.var.name = The name you don't like anymore
# new.var.name = The name you want to get

names(df)[names(df) == 'old.var.name'] <- 'new.var.name'

This code pretty much does the following:

names(df) looks into all the names in the df
[names(df) == old.var.name] extracts the variable name you want to check
<- 'new.var.name' assigns the new variable name.

edited Dec 28 '16 at 23:27

Blaszard

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answered May 10 '13 at 20:33

Side_0o_Effect

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I'm also quite new with R, loved this solution! I've actually checked what it does, and I think it's worth specify that `[names(df) == old.var.name]` actually returns a vector with true/false values. So it has the potential to change multiple column names if, for example, regular expressions are used. – mikyatope Dec 11 '13 at 16:21
3

For regular expression results, use something like `names(df) = sub('pattern', 'replacement', names(df))`. Otherwise you'd be trying to set multiple columns to the same name. – We Are All Monica Sep 27 '14 at 20:09
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Mixed feelings...in a perfect world, where perfect programming languages abound, would it really require this many keystrokes to change the name of a single column? I love R but sometimes I want to strangle it for these types of reasons. – tumultous_rooster Aug 15 '15 at 01:19
Other simple option in accordance to above solution is to simply refer to the column number of the file you want to change the name . That is : # 'Column#1' is the one you want to change the name in your data frame(df) so simply write : `names(df)[1] – Daniel Feb 06 '17 at 15:35
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How there not a wrapper function for this in base? – ifly6 Sep 06 '18 at 17:03
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How we all wish ! I do not know about now, but back then there was not any wrapper in base – Side_0o_Effect Sep 20 '18 at 11:07
Beware of the order of appearance when you are changing multiple columns at the same time (one line of code) use this solution. – Jason Goal Jul 09 '19 at 19:11

score 425 · Accepted Answer · answered Sep 23 '11 at 17:01

425

colnames(trSamp)[2] <- "newname2"

attempts to set the second column's name. Your object only has one column, so the command throws an error. This should be sufficient:

colnames(trSamp) <- "newname2"

answered Sep 23 '11 at 17:01

Joshua Ulrich

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.@JoshuaUlrich - This doesn't seem to work if the column name is something like `"A,B,C,X,Y,Z"` where I want to rename it to `Y` using `testData[379] – Chetan Arvind Patil Jan 17 '19 at 16:10

score 104 · Answer 3 · answered May 05 '14 at 14:53

104

colnames(df)[colnames(df) == 'oldName'] <- 'newName'

answered May 05 '14 at 14:53

zongshiwujie

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I like this solution as you can reference the column name by name, as opposed to requiring to know which number column it is. Better for larger number features. – Cybernetic Aug 22 '14 at 17:18
1

I've got a small extension to the question and this answer. I have a dataframe with a column which has the letters _'snp'_ in it. I want to rename it to _'Marker'_. But I want to use a _regular expression_ to do so. Apparently the code I have is flawed: `colnames(GWASDATA_RAWSELECTION)[colnames(GWASDATA_RAWSELECTION)=="^snp$"] – Sander W. van der Laan Nov 29 '16 at 22:13

score 88 · Answer 4 · answered Oct 03 '13 at 21:19

88

This is an old question, but it is worth noting that you can now use setnames from the data.table package.

library(data.table)

setnames(DF, "oldName", "newName")

# or since the data.frame in question is just one column: 
setnames(DF, "newName")

# And for reference's sake, in general (more than once column)
nms <- c("col1.name", "col2.name", etc...)
setnames(DF, nms)

answered Oct 03 '13 at 21:19

Ricardo Saporta

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or ``setNames`` from base R. – PatrickT Mar 04 '19 at 11:08

score 63 · Answer 5 · answered Aug 26 '13 at 16:02

This can also be done using Hadley's plyr package, and the rename function.

library(plyr) 
df <- data.frame(foo=rnorm(1000)) 
df <- rename(df,c('foo'='samples'))

You can rename by the name (without knowing the position) and perform multiple renames at once. After doing a merge, for example, you might end up with:

  letterid id.x id.y
1       70    2    1
2      116    6    5
3      116    6    4
4      116    6    3
5      766   14    9
6      766   14   13

Which you can then rename in one step using:

letters <- rename(letters,c("id.x" = "source", "id.y" = "target"))

  letterid source target
1       70      2      1
2      116      6      5
3      116      6      4
4      116      6      3
5      766     14      9
6      766     14     13

`rename` is now a function in the `dplyr` package as well. – Sam Firke Apr 29 '15 at 17:42 — Sam Firke, Apr 29 '15 at 17:42

score 52 · Answer 6 · edited Jul 23 '17 at 22:24

52

I think the best way of renaming columns is by using the dplyr package like this:

require(dplyr)
df = rename(df, new_col01 = old_col01, new_col02 = old_col02, ...)

It works the same for renaming one or many columns in any dataset.

edited Jul 23 '17 at 22:24

Rich Scriven

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answered Jul 15 '17 at 17:43

Luis Vazquez

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score 19 · Answer 7 · answered Mar 24 '18 at 21:43

I find that the most convenient way to rename a single column is using dplyr::rename_at :

library(dplyr)
cars %>% rename_at("speed",~"new") %>% head     
cars %>% rename_at(vars(speed),~"new") %>% head
cars %>% rename_at(1,~"new") %>% head

#   new dist
# 1   4    2
# 2   4   10
# 3   7    4
# 4   7   22
# 5   8   16
# 6   9   10

works well in pipe chaines
convenient when names are stored in variables
works with a name or an column index
clear and compact

score 14 · Answer 8 · answered Jan 08 '14 at 07:50

14

I like the next style for rename dataframe column names one by one.

colnames(df)[which(colnames(df) == 'old_colname')] <- 'new_colname'

where

which(colnames(df) == 'old_colname')

returns by the index of the specific column.

answered Jan 08 '14 at 07:50

jshepherd

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+1 for giving the user a chance to use the actual old name :) – Jan 27 '14 at 15:13
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What is here the difference compared to @zongshiwujie 's solution? – buhtz Aug 24 '16 at 06:48
`which()` is not necessary. – sindri_baldur Aug 10 '18 at 11:16

score 9 · Answer 9 · answered Jul 24 '20 at 06:57

9

Let df be the dataframe you have with col names myDays and temp. If you want to rename "myDays" to "Date",

library(plyr)
rename(df,c("myDays" = "Date"))

or with pipe, you can

dfNew      <- df %>% 
  plyr::rename(c("myDays" = "Date"))

answered Jul 24 '20 at 06:57

Ebby

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Scottieie · Answer 10 · 2017-03-11T21:19:45.017

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This is likely already out there, but I was playing with renaming fields while searching out a solution and tried this on a whim. Worked for my purposes.

Table1$FieldNewName <- Table1$FieldOldName
Table1$FieldOldName <- NULL

Edit begins here....

This works as well.

df <- rename(df, c("oldColName" = "newColName"))

edited Mar 11 '17 at 21:19

answered Jan 31 '17 at 21:43

Scottieie

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To whoever marked me down, that is fine, but since I am obviously new to doing this, perhaps you could enlighten as to what was wrong with the answer. – Scottieie Feb 02 '17 at 02:56
There's nothing wrong with your answer, besides it not being a oneliner.. that was just a hostile SO user not having the courage to justify his tantrum. – count0 Mar 10 '17 at 19:12
Thanks @count0. It actually is meaningful to have some mana points or whatever to comment on a question, something I have been yet to be able to do. Follow up questions in some cases would be nice as I learn a new skillset. Again. TY. – Scottieie Mar 11 '17 at 21:12
1

we need to give all columns name to use this. – Arpit Sisodia Apr 02 '17 at 08:47
which package does the `rename` function come from? – Diego Mar 19 '20 at 00:40

score 7 · Answer 11 · edited May 23 '17 at 12:26

You can use the rename.vars in the gdata package.

library(gdata)
df <- rename.vars(df, from = "oldname", to = "newname")

This is particularly useful where you have more than one variable name to change or you want to append or pre-pend some text to the variable names, then you can do something like:

df <- rename.vars(df, from = c("old1", "old2", "old3", 
         to = c("new1", "new2", "new3"))

For an example of appending text to a subset of variables names see: https://stackoverflow.com/a/28870000/180892

score 6 · Answer 12 · answered Sep 23 '11 at 16:10

6

Try:

colnames(x)[2] <- 'newname2'

answered Sep 23 '11 at 16:10

NPE

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This is what threw the error that OP asked about (in his edit). It won't work, as the dataframe only has one column. – Sep 23 '11 at 22:05
.@NPE - This doesn't seem to work if the column name is something like `"A,B,C,X,Y,Z"` where I want to rename it to `Y` using `testData[379] – Chetan Arvind Patil Jan 17 '19 at 16:10

score 4 · Answer 13 · answered Jul 29 '12 at 09:55

4

You could also try 'upData' from 'Hmisc' package.

library(Hmisc)

trSamp = upData(trSamp, rename=c(sample.trainer.index..10000. = 'newname2'))

answered Jul 29 '12 at 09:55

ansek

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Very nice! It's is also possible to rename more columns at once: trSamp = upData(trSamp, rename=c(sample.trainer.index..10000. = 'newname2, AnotherColumnName = 'RenameThisColumn')) – FraNut Jul 07 '16 at 13:11

score 3 · Answer 14 · answered Sep 23 '11 at 17:06

3

If you know that your dataframe has only one column, you can use: names(trSamp) <- "newname2"

answered Sep 23 '11 at 17:06

score 2 · Answer 15 · answered Mar 04 '19 at 14:31

The OP's question has been well and truly answered. However, here's a trick that may be useful in some situations: partial matching of the column name, irrespective of its position in a dataframe:

Partial matching on the name:

d <- data.frame(name1 = NA, Reported.Cases..WHO..2011. = NA, name3 = NA)
##   name1 Reported.Cases..WHO..2011. name3
## 1    NA                         NA    NA
names(d)[grepl("Reported", names(d))] <- "name2"
##   name1 name2 name3
## 1    NA    NA    NA

Another example: partial matching on the presence of "punctuation":

d <- data.frame(name1 = NA, Reported.Cases..WHO..2011. = NA, name3 = NA)
##   name1 Reported.Cases..WHO..2011. name3
## 1    NA                         NA    NA
names(d)[grepl("[[:punct:]]", names(d))] <- "name2"
##   name1 name2 name3
## 1    NA    NA    NA

These were examples I had to deal with today, I thought might be worth sharing.

score 1 · Answer 16 · answered Mar 04 '19 at 22:56

1

I would simply change a column name to the dataset with the new name I want with the following code: names(dataset)[index_value] <- "new_col_name"

answered Mar 04 '19 at 22:56

Parthiban M

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score 0 · Answer 17 · answered Dec 18 '18 at 06:58

I would simply add a new column to the data frame with the name I want and get the data for it from the existing column. like this:

dataf$value=dataf$Article1Order

then I remove the old column! like this:

dataf$Article1Order<-NULL

This code might seem silly! But it works perfectly...

score 0 · Answer 18 · edited Mar 28 '20 at 10:08

0

I found colnames() argument easier https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/row%2Bcolnames

select some column from the data frame

df <- data.frame(df[, c( "hhid","b1005", "b1012_imp", "b3004a")])

and rename the selected column in order,

colnames(df) <- c("hhid", "income", "cost", "credit")

check the names and the values to be sure

names(df);head(df)

edited Mar 28 '20 at 10:08

Johannes Konings

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answered Nov 24 '19 at 11:54

Seyma Kalay

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score 0 · Answer 19 · answered May 25 '20 at 20:21

We can use rename_with to rename columns with a function (stringr functions, for example).

Consider the following data df_1:

df_1 <- data.frame(
  x = replicate(n = 3, expr = rnorm(n = 3, mean = 10, sd = 1)), 
  y = sample(x = 1:2, size = 10, replace = TRUE)
)

names(df_1)

#[1] "x.1" "x.2" "x.3" "y"

Rename all variables with dplyr::everything():

library(tidyverse)

df_1 %>% 
  rename_with(.data = ., .cols = everything(.), 
              .fn = str_replace, pattern = '.*', 
              replacement = str_c('var', seq_along(.), sep = '_')) %>% 
  names()

#[1] "var_1" "var_2" "var_3" "var_4"

Rename by name particle with some dplyr verbs (starts_with, ends_with, contains, matches, ...).

Example with . (x variables):

df_1 %>% 
  rename_with(.data = ., .cols = contains('.'), 
              .fn = str_replace, pattern = '.*', 
              replacement = str_c('var', seq_along(.), sep = '_')) %>% 
  names()

#[1] "var_1" "var_2" "var_3" "y"

Rename by class with many functions of class test, like is.integer, is.numeric, is.factor...

Example with is.integer (y):

df_1 %>% 
  rename_with(.data = ., .cols = is.integer, 
              .fn = str_replace, pattern = '.*', 
              replacement = str_c('var', seq_along(.), sep = '_')) %>% 
  names()

#[1] "x.1"   "x.2"   "x.3"   "var_1"

The warning:

Warning messages: 1: In stri_replace_first_regex(string, pattern, fix_replacement(replacement), : longer object length is not a multiple of shorter object length 2: In names[cols] <- .fn(names[cols], ...) : number of items to replace is not a multiple of replacement length

It is not relevant, as it is just an inconsistency of seq_along(.) with the replace function.

score -3 · Answer 20 · answered Jul 24 '19 at 07:55

-3

library(dplyr)
rename(data, de=de.y)

answered Jul 24 '19 at 07:55

SmallChess

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Care to add a bit of why this helps OP's problem? – Guillaume Racicot Jul 24 '19 at 13:30

How to rename a single column in a data.frame?

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