Question

I have a matrix with two columns some of the numbers are the same in both columns, but column 2 also contains some numbers which are not in column 1.

I would like to select those values in column2 that are not in column1 and insert them in column1 in increasing order.

As a start I was thinking of using some matrix operation like matrix[matrix[,1]%in%matrix[,2]

just instead of %in% using something for “not in”.

Here’s the datafile:

https://dl.dropbox.com/u/22681355/example.csv

example<-read.csv("example.csv")

example[,2] contains some numbers which example[,1] does not.

I would like to:

1. search for these numbers using something equivalent to %not in %

Following the answer below I can do the following:

values<-setdiff(example[,2],example[,1]

order<-sort(values)

Answer 1

Like this?

Rgames> foo
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    5    9   13   17
[2,]    2    6   10   14   18
[3,]    3    7    1   15   19
[4,]    4    8    3   16   20
Rgames> foo[,1]%in%foo[,3]
[1]  TRUE FALSE  TRUE FALSE
Rgames> foo[,1]*!foo[,1]%in%foo[,3]
[1] 0 2 0 4

I’m sure there’s a cleaner way. Heck, just do this:

Rgames> setdiff(foo[,1],foo[,3])
[1] 2 4