Dear R forum

Suppose I have a data.frame 

df = data.frame(id = c(1:6), x = c(15, 21, 14, 21, 14, 38), y = c(36, 38, 55, 11, 5, 18), x.1 = c(15, 21, 14, 21, 14, 38), z = c("D", "B", "A", "F", "H", "P"))


> df
  id  x  y    x.1 z
1  1 15 36  15 D
2  2 21 38  21 B
3  3 14 55  14 A
4  4 21 11  21 F
5  5 14  5  14 H
6  6 38 18  38 P


Clearly columns x and x.1 are identical. In reality, I have a large data.frame and can't make out which columns are identical, but I am sure that column with name say x is repeated as x.1, x.2 etc.

How to automatically identify and retain only one column (in this example column x) among the identical columns besides other non-identical columns (viz. id, y and z).


Regards

Katherine

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