Changing column names in R by name not by number

Question

I have a table in R which has many columns. I want to change the column names. I have found that:

colnames(table)[123] <- "newName"

changes the 123rd column to the name "newName". But to achieve this I need to find the number of the column with the name "oldName". I was thinking of something like this:

colnames(table)["oldName"] <- "newName"

but that didn't work. So how can one go about doing this?

Answer 1

It's quite easy using dplyr's rename function:

library(dplyr)
rename(mtcars, cylinders = cyl)

This will rename the column "cyl" to be "cylinders" in the data set "mtcars".

Edit after comment:

If you want to rename multiple columns, you can do (without dplyr):

names(mtcars)[names(mtcars) %in% c("mpg", "cyl", "hp")] <- c("miles", "cylinders", "horsepower")
names(mtcars)
# [1] "miles"      "cylinders"  "disp"       "horsepower" "drat"      
# [6] "wt"         "qsec"       "vs"         "am"         "gear"      
#[11] "carb" 

So you just need 1 line to rename multiple columns. And of course, you could store those names in vectors.

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Note to whom it may concern: while it is true that plyr has a rename function, dplyr also has a rename function in its current CRAN version 0.3.0.2. It is described in the introduction to dplyr and, if you're running the current version, you can just type ?dplyr::rename . If you look closely, you can even tell which one is being used because there's a subtle difference between plyr's and dplyr's rename functions: in plyr, it would be plyr::rename(mtcars, c("oldName" = "newName")) while in dplyr (like in my answer) it is dplyr::rename(mtcars, newName = oldName) .

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Edit after comment by OP:

I cannot reproduce the error you describe. Here's what I understood you did, but it works without any errors or unexpected behavior in my case:

df <- data.frame(DE9 = 1:2, code9 = 3:4)
df
#  DE9 code9
#1   1     3
#2   2     4
dplyr::rename(df, newname = DE9)
#  newname code9
#1       1     3
#2       2     4

Answer 2

see if this suits you

library(data.table)
cars = setnames(as.data.table(mtcars),
                c("mpg", "cyl", "hp"),  # old column names
                c("miles", "cylinders", "horsepower"))  # corresponding new column names
names(cars)
# [1] "miles"      "cylinders"  "disp"       "horsepower" "drat"       "wt"        
# [7] "qsec"       "vs"         "am"         "gear"       "carb"
setDF(cars) # convert back to data.frame if needed.

Answer 3

colnames(table)[colnames(table)=="V1"] <- "VeeOne"

If you want to stick to base R (data table and dplyr can be tricky for beginners, and besides, grep can misfire badly if you have similar column names), just use the above.

Full replicable example:

table <- matrix(1:100, ncol=10)  
colnames(table) <- paste0("V",1:10)  
colnames(table)  
colnames(table)[colnames(table)=="V1"] <- "VeeOne"  
colnames(table)

Answer 4

It's not dplyr you are after as been posted here, as, according to the reference manual, it does not include rename . It is instead plain plyr that includes rename . And it can take a name character vector for renaming:

library(plyr)
rename(mtcars, c("cyl"="cylinders", "mpg"="miles per gallon", "hp"="horsies"))