From: Heather Turner <Heather.Turner_at_warwick.ac.uk>

Date: Mon 20 Jun 2005 - 23:01:07 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Jun 20 23:49:38 2005

Date: Mon 20 Jun 2005 - 23:01:07 EST

Dr H Turner

Research Assistant

Dept. of Statistics

The University of Warwick

Coventry

CV4 7AL

>>> Robin Hankin <r.hankin@noc.soton.ac.uk> 06/20/05 10:32am >>> Hi

I had a hard-to-find bug in some of my code the other day, which I
eventually

traced to my misusing of sweep().

I would expect sweep() to give

me a warning if the elements don't recycle nicely, but

X <- matrix(1:36,6,6)

sweep(X,1,1:5,"+")

[,1] [,2] [,3] [,4] [,5] [,6]

[1,] 2 9 16 23 30 32

*[2,] 4 11 18 25 27 34
**[3,] 6 13 20 22 29 36
**[4,] 8 15 17 24 31 38
**[5,] 10 12 19 26 33 40
**[6,] 7 14 21 28 35 37
*

gives no warning, even though (5,36)=1.

Also,

sweep(X,1,c(1,1000),"+")

and

sweep(X,2,c(1,1000),"+")

...which is also expected since the matrix is square. Perhaps the
following will help you see why:

> matrix(1:5,6,6)

[,1] [,2] [,3] [,4] [,5] [,6]

*[1,] 1 2 3 4 5 1
**[2,] 2 3 4 5 1 2
**[3,] 3 4 5 1 2 3
**[4,] 4 5 1 2 3 4
*

[5,] 5 1 2 3 4 5

[6,] 1 2 3 4 5 1

Warning message:

data length [5] is not a sub-multiple or multiple of the number of rows

[6] in matrix

> matrix(1:5,6,6, byrow = TRUE)

[,1] [,2] [,3] [,4] [,5] [,6]

*[1,] 1 2 3 4 5 1
**[2,] 2 3 4 5 1 2
**[3,] 3 4 5 1 2 3
**[4,] 4 5 1 2 3 4
*

[5,] 5 1 2 3 4 5

[6,] 1 2 3 4 5 1

Warning message:

data length [5] is not a sub-multiple or multiple of the number of rows

[6] in matrix

i.e. recycling a vector of length 5 down the columns gives the same
result as recycling the same vector along the rows.

Heather

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Jun 20 23:49:38 2005

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