[R] sweep?

[David Winsemius]

Either the rows or columns have a (possibly) varying argument vector  
applied with an operator. The default operator is "-"/

 > dtest <- matrix(1:25, nrow=5)
 > dtest
      [,1] [,2] [,3] [,4] [,5]
[1,]    1    6   11   16   21
[2,]    2    7   12   17   22
[3,]    3    8   13   18   23
[4,]    4    9   14   19   24
[5,]    5   10   15   20   25
 > sweep(dtest, 2, 1)
      [,1] [,2] [,3] [,4] [,5]
[1,]    0    5   10   15   20     # -1 argument recycling
[2,]    1    6   11   16   21
[3,]    2    7   12   17   22
[4,]    3    8   13   18   23
[5,]    4    9   14   19   24
 > sweep(dtest, 2, 1:5)
      [,1] [,2] [,3] [,4] [,5]
[1,]    0    4    8   12   16    # -1 -2 -3 -4 -5
[2,]    1    5    9   13   17    #      |
[3,]    2    6   10   14   18    #      |
[4,]    3    7   11   15   19    #     \/
[5,]    4    8   12   16   20
 > sweep(dtest, 1, 1:5)
      [,1] [,2] [,3] [,4] [,5]
[1,]    0    5   10   15   20    # -1 --->
[2,]    0    5   10   15   20    # -2
[3,]    0    5   10   15   20    # -3
[4,]    0    5   10   15   20    # -4
[5,]    0    5   10   15   20    # -5

 > sweep(dtest, 1, 1:5, FUN="+")
      [,1] [,2] [,3] [,4] [,5]
[1,]    2    7   12   17   22   # +1
[2,]    4    9   14   19   24   # etc
[3,]    6   11   16   21   26
[4,]    8   13   18   23   28
[5,]   10   15   20   25   30
On Mar 16, 2009, at 10:25 PM, <rkevinburton at charter.net> <rkevinburton at charter.net 
 > wrote:

> I am having a hard time understanding just what 'sweep' does. The  
> documentation states:
>
> Return an array obtained from an input array by sweeping out a  
> summary statistic.
>
> So what does it mean "weeping out a summary statistic"?
>
> Thank you.
>
> Kevin
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT