Perhaps along these lines:
1st #need to decide what your group width is , so the second number
inside the extraction call will be that number minus 1:
for (x in seq(1:1000, by=6) {
temp <- na,omit( shp[x:(x+5), ] ) # Need the parens in x:(x+5)
lm( formula, data=temp)
}
Or depending on what you actually meant:
for (x in seq(1:1000, by=5) {
temp <- shp[ x:(x+4), which(!is.na(shp[x:x+4, ]))]
lm( formula, data=temp)
}
But I do feel compelled to ask: Do you really get meaningful
information from lm applied to 5 cases? Especially when the predictors
used may not be the same from subset to subset???
--
David
On Nov 24, 2009, at 3:25 PM, Jim Bouldin wrote:
I want to perform linear regression on groups of consecutive rows--
say 5 to
10 such--of two matrices. There are many such potential groups
because the
matrices have thousands of rows. The matrices are both of the form:
shp[1:5,16:20]
SL495B SL004C SL005C SL005A SL017A
-2649 1.06 0.56 NA NA NA
-2648 0.97 0.57 NA NA NA
-2647 0.46 0.30 NA NA NA
-2646 0.92 0.48 NA NA NA
-2645 0.82 0.48 NA NA NA
That is, they both have NA values, and non-NA values, in the same
matrix
positions. In my attempts so far, I have had two problems. First, in
using the split function (which I assume is essential here), I am
unable to
split the matrices by groups of rows (say rows 1 to 5, 6 to 10, etc):
shp_split = split(shp,row(shp))
will split the matrix by rows but not by groups thereof. Stumped.
Second, I cannot seem to get rid of the NA values, which would
prevent the
regression even is I could figure out how to split the matrices
correctly,
e.g.:
shp_split = split(shp,row(shp))
shp_split = shp_split[!is.na(shp_split)]
shp_split[1]
$`1`
[1] 0.68 0.28 0.43 0.47 0.64 0.40 0.69 0.56 0.62 0.40 1.01 0.67
0.17 1.36
1.84 1.06 0.56 NA NA NA NA NA NA NA NA NA NA
NA NA
NA NA NA etc
IF I solve these problems, will I in fact be able to perform
individual
linear regressions on the (numerous) collections of 5 to 10 rows?
Thanks as always for any insight.
Jim Bouldin
Research Ecologist
Department of Plant Sciences, UC Davis
Davis CA, 95616
530-554-1740
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
