Replicating the rows of a table n times each

["Tzamouranis, Ioannis C" <Ioannis.Tzamouranis@constellation.com>]

Thanks to all the folks that pointed out easy ways to do this.

The question was:

Other than looping to produce this, is there a way to replicate the rows of a table n times each so that a table such as:

1 2 3 4

A B C D

5 6 7 8

a b c d

become

1 2 3 4

1 2 3 4

1 2 3 4

A B C D

A B C D

A B C D

5 6 7 8

5 6 7 8

5 6 7 8

a b c d

a b c d

a b c d

(where in this case n=3)?

For an answer, I quote Chris Green, although many others (Chris Baker, Christos Hatzis, Brad Biggerstaff and Thomas Jagger among them) gave equally good and similar answers:

Just use an index vector:

> z <- rbind(1:4,letters[1:4],5:8,upperCase(letters[1:4]))

> z

     [,1] [,2] [,3] [,4]

[1,] "1"  "2"  "3"  "4"

[2,] "a"  "b"  "c"  "d"

[3,] "5"  "6"  "7"  "8"

[4,] "A"  "B"  "C"  "D"

> z[rep(1:4,each=3),]

      [,1] [,2] [,3] [,4]

 [1,] "1"  "2"  "3"  "4"

 [2,] "1"  "2"  "3"  "4"

 [3,] "1"  "2"  "3"  "4"

 [4,] "a"  "b"  "c"  "d"

 [5,] "a"  "b"  "c"  "d"

 [6,] "a"  "b"  "c"  "d"

 [7,] "5"  "6"  "7"  "8"

 [8,] "5"  "6"  "7"  "8"

 [9,] "5"  "6"  "7"  "8"

[10,] "A"  "B"  "C"  "D"

[11,] "A"  "B"  "C"  "D"

[12,] "A"  "B"  "C"  "D"

> 

The rep(1:4, each=3) expands to (1,1,1,2,2,2,3,3,3,4,4,4), so each row of the input will be repeated 3 times. Just change the "4" to the number of rows in the input (or nrow(z)) and the 3 to the number to times to replicate each row.

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