df = data.frame(a = c(1, 3, 9, 0),
b = c(12, 98, 90, 20),
c = c(2, 4, 6, 8),
row.names = c('o', 'p', 'q', 'r'))
print(df)
df$x = c("r", "c#", "c", "c++")
df$y = c("python", "java", "javascript", "cobol")
print(df)
# run:
#
# a b c
# o 1 12 2
# p 3 98 4
# q 9 90 6
# r 0 20 8
# a b c x y
# o 1 12 2 r python
# p 3 98 4 c# java
# q 9 90 6 c javascript
# r 0 20 8 c++ cobol
#