[R] NA's when subset in a dataframe
Milan Bouchet-Valat
nalimilan at club.fr
Thu May 3 23:33:48 CEST 2012
Le jeudi 03 mai 2012 à 07:37 -0700, agent dunham a écrit :
> Dear community,
>
> I'm having this silly problem.
>
> I've a linear model. After fixing it, I wanted to know which data had
> studentized residuals larger than 3, so i tried this:
>
> d1 <- cooks.distance(lmmodel)
> r <- sqrt(abs(rstandard(lmmodel)))
> rstu <- abs(rstudent(lmmodel))
>
> a <- cbind( mydata, d1, r,rstu)
>
> alargerthan3 <- a[rstu >3, ]
>
> And suddenly a[rstu >3, ] has 17 rows, 7 of them are "new rows", where all
> the entries are NA's, even its rownames.
>
> Because of this I'm not sure of the dimension of a[rstu >3, ] (Do I only
> have 8 entries?)
>
> Has this happened to anybody before? If so, why this extra NA rows? what's
> the problem? Is there any other way to know which data have studentized
> residuals larger than 3?
>
>
> if it's needed to upload my data, just tell me.
A small reproducible example would have been better. Anyway, see page 88
of The R Inferno.
In your case, the simplest solutions are to do:
alargerthan3 <- a[which(rstu > 3),]
or
alargerthan3 <- subset(a, rstu > 3)
Cheers
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