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] 

Answer 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.

Answer 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"