[R] Eliminate cases in a subset of a dataframe
James W. MacDonald
jmacdon at med.umich.edu
Mon Sep 14 19:02:49 CEST 2009
linmod2 <- update(linmod, data = subdata[-c(11,22,33),])
Hollix wrote:
> Hi folks,
>
> I created a subset of a dataframe (i.e., selected only men):
>
> subdata <- subset(data,data$gender==1)
>
> After a residual diagnostic of a regression analysis, I detected three
> outliers:
>
> linmod <- lm(y ~ x, data=subdata)
> plot(linmod)
>
> Say, the cases 11,22, and 33 were outliers.
>
> Here comes the problem: When I want to exclude these three cases in a
> further regression analysis,
> - for instance with linmod2 <- lm(y[-c(11,22,33)] ~ x[-c(11,22,33)],
> data=subdata) - it does not work.
>
> I guess this has something to do with this strange "row.names"-vector which
> has been added to the dataframe when creating the subset. I find it very
> strange why R gives the case numbers in the diagnostics but then doesn't
> allow me to use these numbers for further exclusion.
>
> Can anybody tell me:
> 1. what this row.names vector is
> 2. How I can refer to cases after creating a subset (e.g., in order to
> exclude them).
>
> Many thanks in advance,
> Best,
> Holger
--
James W. MacDonald, M.S.
Biostatistician
Douglas Lab
University of Michigan
Department of Human Genetics
5912 Buhl
1241 E. Catherine St.
Ann Arbor MI 48109-5618
734-615-7826
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