Disclaimer/Apology: I am an R newbie

I am seeing some behaviour that seems to me to be the result of some
cacheing going on at some level, and perhaps this is expected behaviour. I
would just like to understand the basic rules.

What I have is a file with some data. I read it in and then do a summary on
the resulting dataframe. I find the some values are completely outside the
expected range, these value need to be dropped from further analysis as
erroneous observations (yes, I apologize to the purists in advance :-) ).

If I do this and read the file again, then circlesPlot (from fBasics) two of
the columns in the data, then the plot is not updated. The outlier point is
still there. However, when I detach and reattach the dataframe, it seems to
work okay. For example,
# Plot has the outlier point in it.
# Edit the file, commenting out the outlier line, save, then...
> SG <- read.table
("c:/Vivek/MFC/Data/SG/combinedSG.tdf",header=TRUE,sep="\t")
> SGm2 <- lm(A3Yr ~ A10Holdings, data=SG)
> circlesPlot(A10Holdings,A3Yr, size=NetAssets)
> abline(coef(SGm2)) # Put the regression line on the plot
> SG <- read.table
("c:/Vivek/MFC/Data/SG/combinedSG.tdf",header=TRUE,sep="\t")
> summary(SG) #Outlier does not show in the summary
> circlesPlot(A10Holdings,A3Yr, size=NetAssets) # ... But Plot still has the
outlier
> detach(SG)
> attach(SG)
> circlesPlot(A10Holdings,A3Yr, size=NetAssets) # Outlier is gone from the
plot

So, here are my questions:
1. Is there a simpler / more idiomatic way in R, than commenting out the
data in the data file to exclude some outliers in the data (i.e. to do data
trimming). In EViews this is done by setting the sample.
2. Is the "flushing" of the cache happening as a result of the
detach/attach, or some other reason?

Thanks for any help,

Vivek Satsangi

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