R help - Jun 2010 - Remove observations deemed influential by influential.measure

dbs is an existing dataframe. I fit a lm and looked at influential
observations. I want now to delete the influential observations from dbs,
fit another lm, and see how different the results are. What is the syntax to
remove the influential observations from dbs?

fit <- lm(NI ~ PG + log(TG), data=dbs)
fit.influential.observations <- influence.measures(fit)

dbs.without.influential.observations <- ?????

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On Jun 29, 2010, at 1:10 PM, GL wrote:
>
> dbs is an existing dataframe. I fit a lm and looked at influential
> observations. I want now to delete the influential observations from  
> dbs,
> fit another lm, and see how different the results are. What is the  
> syntax to
> remove the influential observations from dbs?
>
> fit <- lm(NI ~ PG + log(TG), data=dbs)
> fit.influential.observations <- influence.measures(fit)
>
> dbs.without.influential.observations <- ?????
>
Look (more?) carefully at the examples on the help page. The first  
example shows how to extract a vector of row numbers associated with  
infuential cases. If you need help applying htat information to a  
dataframe using "[" then you probably need to re-read the Introduction
to R as well.

-- 

David Winsemius, MD
West Hartford, CT

dbs_influential_obs <- which(apply(fit.influential.observations$is.inf, 1,
any))
dbs_sans_influential_obs <- dbs1[-dbs_influential_obs,]

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