On Dec 15, 2010, at 11:19 AM, Gerrit Eichner wrote:
Hello, Vassilis,
maybe
with( test.df, ave( vector, factor, FUN = function( x) x - mean( x)))
does what you want.
THere is also the scale function which can be called with the
parameters set to center but not scale the results:
with( test.df, ave( vector, factor, FUN=scale, scale=FALSE)) #
center=TRUE is default.
--
David.
-- Gerrit
On Wed, 15 Dec 2010, Vassilis wrote:
I would like to de-mean the 'vector' column of the following
dataframe by
factor:
set.seed(5444)
vector <- rnorm(1:10)
factor <- rep(1:2,5)
test.df <- data.frame(factor, vector)
which is:
factor vector
1 1 -0.4963935
2 2 -2.0768182
3 1 -1.5822224
4 2 0.8025474
5 1 0.3504199
6 2 0.2358464
7 1 -0.3989443
8 2 -0.3692544
9 1 -0.3174586
10 2 1.4305431
Using the by() command, I get:
by(test.df$vector, test.df$factor, function(x) {x - mean(x)})
test.df$factor: 1
[1] -0.007473699 -1.093302612 0.839339673 0.089975488 0.171461151
--------------------------------------------------------------------------------------------------
test.df$factor: 2
[1] -2.0813911 0.7979745 0.2312735 -0.3738272 1.4259702
My question is: Is there a way to have this output put back to the
dataframe? I.e to make by(), or some other command, return me a
vector of
length 10 whose values x' correspond to x'_1 = x_1 - mean(x |
factor1), x'_2
= x_2 - mean(x | factor2),...
Thanks in advance for the help, and apologies for the poor notation.
Vassilis
--
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______________________________________________
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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
West Hartford, CT
______________________________________________
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