CODEWITHSUNDEEP
ralgorithm
annievic
annievic

Reputation: 411

Using R to randomly pair elements not in the same group

I'm writing an algorithm in R to randomly pair people up but people in the pair cannot be from the same group (team).

I've started by creating an nxn matrix of all of the people. I've marked 0 to indicate people that cannot be paired together (if they are in the same team) and 1 otherwise.

The problem: I now need to sample from the list of eligible people (all of the 1s) in each row, and make a note of the pairing and make sure that the two people in that pair cannot now be paired with another person.

e.g.

Name - Team

A - 1

B - 2

C - 3

D - 4

E - 1

F - 2

G - 1

  A B C D E F G
A 0 1 1 1 0 1 0
B 1 0 1 1 1 0 1
C 1 1 0 1 1 1 1
D 1 1 1 0 1 1 1
E 0 1 1 1 0 1 0
F 1 0 1 1 1 0 1
G 0 1 1 1 0 1 0

I realise that this algorithm may get stuck if we get to a stage where nobody can be matched together, so I was thinking of incorporating a timer to restart when the algorithm has been running for say 5 minutes.

Happy to consider any other matching algorithms that you think may be more suitable.

I've already had a look at similar problems on stack overflow (e.g. Sampling column values in a matrix, without replacement) but none of them seem to address the problem of not pairing people from the same group.

Thank you.

Upvotes: 4

Views: 417

Answers (1)

akrun
akrun

Reputation: 887038

Try

 (!tcrossprod(table(df1)))+0L

data

df1 <- structure(list(Name = c("A", "B", "C", "D", "E", "F", "G"), 
Team = c(1L, 
2L, 3L, 4L, 1L, 2L, 1L)), .Names = c("Name", "Team"),
 class =  "data.frame", row.names = c(NA, -7L))

Upvotes: 5

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