Assigning colnames() to specific column of a data frame

Question

I have a question about the colnames function in the base package

Let\'s say you have a data.frame, as follows:

df <- data.frame(var         


        

Answer 1

Call the colnames() function on the dataframe (the entire dataframe) then access by indexing, the items of the 1D vector returned by that function call:

> data(Orange)    
> Orange[1:5,]
  Tree  age circumference
1    1  118            30
2    1  484            58
3    1  664            87
4    1 1004           115
5    1 1231           120
> call *colnames* on the Orange dataframe and bind it to the variable *cn*
> cn = colnames(Orange)
> cn    
[1] "Tree"          "age"           "circumference"
> length(cn)
[1] 3
> class(cn)
 [1] "character"

> # access the items of this 1D character vector by index:
> cn[1]
[1] "Tree"
> cn[3]
[1] "circumference"
> # likewise modify any item the same way:
> cn[3] = '2*pi*r'