From: Leo Gürtler <leog_at_anicca-vijja.de>

Date: Fri 03 Feb 2006 - 00:31:35 EST

Date: Fri 03 Feb 2006 - 00:31:35 EST

(Ted Harding) schrieb:

Dear Elizabeth,

the R-package "mice" has

?md.pattern

and "Hmisc" also contains some software to describe missing data. I think both do not have limitations like prelim.norm.

best wishes,

leo

>On 01-Feb-06 Ted Harding wrote:

*>
**>
**>>On 01-Feb-06 Elizabeth Lawson wrote:
**>>
**>>
**>>>Hey eveyone! I hope someone can help wiht this question. I have a
**>>>matirux of all zeros and ones and I would like to indentify all unique
**>>>patterns in the rows andthe number of times the pattern occurs. I
**>>>changed all zeros to NA tried to use prelim.norm to identify all
**>>>patterns of missing data in the rows. I got the message
**>>>
**>>> Warning message:
**>>>NAs introduced by coercion
**>>>
**>>> Any ideas of how to get this to work? Or are there any way to
**>>>indentify all the unique patterns in a huge matrix? ( 10000 x 71)
**>>>
**>>> Thanks for any suggestions!!
**>>>
**>>> Elizabeth Lawson
**>>>
**>>>
**>>I think Chuck Celand has pretty well answered it: Don't worry
**>>about the warning, since I'm pretty sure it is generated when
**>>prelim.norm is calculating something else (e.g. the covariance
**>>matrix) and it is not related to generating prelim.norm(X)$r
**>>which is the list of patterns and the numbers of times they occur.
**>>
**>>Best wsihes,
**>>Ted.
**>>
**>>
**>
**>Sorry -- I should have read the detail of your original message
**>more carefully. In short, you have too many columns for prelim.norm
**>to work.
**>
**>The long answer: prelim.norm analyses the missing data patterns
**>by representing the locations of NAs as integers, where the jth
**>bit in the binary representation of the integer is 1 for an NA,
**>0 for a non-NA. Hence the representation of the pattern runs out
**>of steam when there are more than a certain number of columns,
**>corresponding to the highest power of 2 that can be represented
**>as an integer in R.
**>
**> .Machine$integer.max
**> [1] 2147483647
**>
**> 2^31 -1
**> [1] 2147483647
**>
**>so that prelim.norm can only encode NA-patterns in an R integer
**>for up to 31 columns. More than that, and it will not work properly
**>or at all.
**>
**>Check:
**>
**> X<-matrix(sample(c(0,1),87,replace=TRUE),ncol=29)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (no warning, 3 rows)
**>
**> X<-matrix(sample(c(0,1),90,replace=TRUE),ncol=30)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (no warning, 3 rows)
**>
**> X<-matrix(sample(c(0,1),93,replace=TRUE),ncol=31)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (no warning, 3 rows)
**>
**> X<-matrix(sample(c(0,1),93,replace=TRUE),ncol=32)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (3 rows, "Warning message: NAs introduced by coercion")
**>
**> X<-matrix(sample(c(0,1),93,replace=TRUE),ncol=33)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (2 rows, "Warning message: NAs introduced by coercion")
**>
**> X<-matrix(sample(c(0,1),93,replace=TRUE),ncol=34)
**> Y<-X; Y[Y==0]<-NA
**> prelim.norm(Y)$r
**> [...] (1 row, "Warning message: NAs introduced by coercion")
**>
**>(Try a few of these for yourself; it is very unlikely that you get
**>one 1 or 2 distinct rows when you have 3 rows of 30+ 0s and 1s
**>sampled at random).
**>
**>A similar issue came up some time ago (I can't locate the thread
**>in the archive at the moment) in vennection with the 'mix'
**>package.
**>
**>However, you can have as many columns as you like if you use
**>'unique' to identify the distinct patterns of 0s and 1s, rather
**>than using 'prelim.norm'.
**>
**>Hoping this helps,
**>Ted.
**>
**>
**>
**>--------------------------------------------------------------------
**>E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk>
**>Fax-to-email: +44 (0)870 094 0861
**>Date: 02-Feb-06 Time: 01:42:13
**>------------------------------ XFMail ------------------------------
**>
**>______________________________________________
**>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
**>
**>
**>
*

-- email: leog@anicca-vijja.de www: http://www.anicca-vijja.de/ ______________________________________________ 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.htmlReceived on Fri Feb 03 00:38:37 2006

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