get all the column names in r code example

Example 1: r type of all columns

sapply(my.data, class)
        y        x1        x2        X3 
"numeric" "integer" "logical"  "factor"

Example 2: how to change column names in r

R> X <- data.frame(bad=1:3, worse=rnorm(3))
R> X
  bad     worse
1   1 -2.440467
2   2  1.320113
3   3 -0.306639
R> colnames(X) <- c("good", "better")
R> X
  good    better
1    1 -2.440467
2    2  1.320113
3    3 -0.306639