On Aug 16, 2011, at 1:10 PM, Stuart Luppescu wrote:
Hello all, I need to extract rows and columns from a data frame and
put
them in a matrix. In some cases, there are no rows in the data frame
meeting the selection criteria. For those rows I want to put a row of
0's in the matrix. Here's my clumsy code:
tab1.m1 <- matrix(0, nrow=2, ncol=4)
tab1.m1[1,] <- ifelse(length(as.matrix(tab1[tab1$comp==the.comp &
tab1$schlid==the.schl & tab1$ext.obs==0, 4:7])) > 0,
as.matrix(subset(tab1, tab1$comp==the.comp & tab1$schlid==the.schl &
tab1$ext.obs==0)[4:7]),
Missing comma about here
-----------------------------------------------------------------^
0)
The row of data I want to put in the matrix is:
tab1[tab1$comp==the.comp & tab1$schlid==the.schl & tab1$ext.obs==0,]
schlid ext.obs comp 1 2 3 4 NA
41 22091 0 1 0.04166667 0.04166667 0.7083333 0.2083333 0
If I do this:
tab1.m1[1,] <- as.matrix(subset(tab1, tab1$comp==the.comp &
tab1$schlid==the.schl & tab1$ext.obs==0)[4:7])
I get the correct values in the matrix:
tab1.m1[1,] <- as.matrix(subset(tab1, tab1$comp==the.comp &
tab1$schlid==the.schl & tab1$ext.obs==0)[4:7])
tab1.m1
[,1] [,2] [,3] [,4]
[1,] 0.04166667 0.04166667 0.7083333 0.2083333
[2,] 0.00000000 0.00000000 0.0000000 0.0000000
but when I use the ifelse() as above, I get this:
[,1] [,2] [,3] [,4]
[1,] 0.04166667 0.04166667 0.04166667 0.04166667
[2,] 0.00000000 0.00000000 0.00000000 0.00000000
Can anyone explain this to me?
Also, is there an easier, less clumsy way to test for the existence
of a
row in a data frame?
Thanks in advance.
--
Stuart Luppescu -=- slu .at. ccsr.uchicago.edu
University of Chicago -=- CCSR
才文と智奈美の父 -=- Kernel 2.6.39-gentoo-r3
You can't expect statistical procedures to rescue
you from poor data. -- Berton Gunter (on
dealing with missing values in a cluster analysis)
R-help (April 2005)
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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