try this:

mat <- matrix(rnorm(20), 5, 4,
    dimnames = list(letters[1:5], LETTERS[1:4]))
mat[sample(20, 4)] <- NA

ind <- which(is.na(mat), arr.ind = TRUE)
mat
cbind(RowName = rownames(mat)[ind[, 1]],
    ColName = colnames(mat)[ind[, 2]])



I hope it helps.

Best,
Dimitris


On 10/8/2010 7:09 AM, Data Analytics Corp. wrote:
Hi,

Suppose I have a 3X4 matrix with row names TL, JAR and TM and column
names A, B, C, D. The cell in the first row, third column has an NA. I
want to find the row and column NAMES corresponding to that cell with
the NA. Obviously, I want to extend this to any matrix of any size that
has one or more cells with NAs. Any suggestions?

Thanks,

Walt

________________________

Walter R. Paczkowski, Ph.D.
Data Analytics Corp.
44 Hamilton Lane
Plainsboro, NJ 08536
________________________
(V) 609-936-8999
(F) 609-936-3733
w...@dataanalyticscorp.com
www.dataanalyticscorp.com

_____________________________________________________



--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/

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