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

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]

Solution 1:

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:

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

Solution 2:

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"

Solution 3:

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

Solution 4:

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)