Hi
You put NA to some variable in 150 rows. So you do not have "mysterious" NA
rows in your file. If you want to select anything based on column with NA
values you have to perform your selection using which (as Rui suggested).
It is documented in help page, although it is probably rather less
comprehensible (maybe some example added to help page could be useful).
-----
NAs in indexing
When extracting, a numerical, logical or character NA index picks an unknown
element and so returns NA in the corresponding element of a logical, integer,
numeric, complex or character result, and NULL for a list. (It returns 00 for a
raw result.)
-----
I believe that this behaviour has some reason, because you compare 2 to NA and
NA is basically "I do not know". So it could be 2 and therefore also rows with
NA are returned. If I am wrong, I hope R gurus will correct me.
You said you want to remove rows with NA values, therefore I suggested
complete.cases function. After this you end with object stripped from rows with
NA values so with less rows.
I would be rather cautious with word "errorneous". I remember old days when
Excel considered empty cells as zeros and gave "errorneous" calculations but I
believe that it was pretty sensible from accountant point of view as empty cell
means 0.
In almost all cases, analysis in R give you correct results, you just need to
tell R how to apply function to object with NA values.
> mean(t1$Petal.Width)
[1] NA
> mean(t1$Petal.Width, na.rm=T)
[1] 1.147101
>
Cheers
Petr
> -----Original Message-----
> From: Ernest Han <ernest....@gmail.com>
> Sent: Wednesday, January 16, 2019 3:27 AM
> To: PIKAL Petr <petr.pi...@precheza.cz>
> Cc: r-help@r-project.org
> Subject: Re: [R] NA rows appeared in data.frame
>
> Dear Rui and Petr,
>
> Thank you for taking time and effort to help.
>
> Rui's solution is an effective workaround so that I can continue to work with
> the data. However, the appearance of these NA rows (with NA
> rownames) is clearly errorneous (possibly a bug behaviour due to R base code).
> What I am interested is a solution that removes these NA rows.
>
> The reasons is because (1) prior to the NA assignment, one does not need to
> test for NA value. (2) Besides, sometimes these NA values are needed as part
> of
> the data to indicate that the missing data.
>
> > t1[t1$Petal.Width==1.8, "Petal.Width"] <- NA
>
> Petr's solution is also not apt in my case, because it removes 12 rows that
> have
> NA values in "Petal.Width". I would like a solution that keeps the 150 rows,
> but
> not the mysterious 12 rows with all NA values in all columns.
Now I am puzzled what do you really want?
with your example and my suggestion you get
t1 <- iris
t1[t1$Petal.Width==1.8, "Petal.Width"] <- NA
t2 <- t1[!is.na(t1$Petal.Width),]
t2[t2$Petal.Width == 2.0, ]
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
111 6.5 3.2 5.1 2 virginica
114 5.7 2.5 5.0 2 virginica
122 5.6 2.8 4.9 2 virginica
123 7.7 2.8 6.7 2 virginica
132 7.9 3.8 6.4 2 virginica
148 6.5 3.0 5.2 2 virginica
>
> dim(t2)
[1] 138 5
> dim(t1)
[1] 150 5
>
>
> Once again, I appreciate your suggestions and I am hoping that this
> 'errorneous'
> behaviour has a fix.
>
> Cheers,
> Ernest
>
> On Mon, Jan 14, 2019 at 4:25 PM PIKAL Petr <petr.pi...@precheza.cz> wrote:
> >
> > Hi
> >
> > If you want to remove rows with NA values from your data you could use
> >
> > ?complete.cases
> >
> > or
> >
> > t2 <- t1[!is.na(t1$Petal.Width),]
> >
> > Cheers
> > Petr
> >
> > > -----Original Message-----
> > > From: R-help <r-help-boun...@r-project.org> On Behalf Of Rui
> > > Barradas
> > > Sent: Saturday, January 12, 2019 12:55 PM
> > > To: Ernest Han <ernest....@gmail.com>; r-help@r-project.org
> > > Subject: Re: [R] NA rows appeared in data.frame
> > >
> > > Hello,
> > >
> > > You have to test for NA. Some (12) of the values of t1$Petal.Width
> > > are NA therefore t1$Petal.Width == 2.0 alone returns 12 NA values.
> > >
> > > t1[t1$Petal.Width == 2.0 & !is.na(t1$Petal.Width == 2.0), ]
> > >
> > > Or use which(t1$Petal.Width == 2.0).
> > >
> > > t1[which(t1$Petal.Width == 2.0), ]
> > >
> > >
> > > Hope this helps,
> > >
> > > Rui Barradas
> > >
> > > Às 08:23 de 12/01/2019, Ernest Han escreveu:
> > > > Dear All,
> > > >
> > > > After replacing some values in a data.frame, NAs rows have
> > > > appeared and cannot be removed. I have googled these issues and
> > > > found that several people have encountered it. Solutions in
> > > > stackoverflow seem to provide work-arounds but does not remove it from
> the data.frame.
> > > > Therefore, I am turning to experts in this community for help.
> > > >
> > > > The code is as follows,
> > > >
> > > >> t1 <- iris
> > > >> t1[t1$Petal.Width==1.8, "Petal.Width"] <- NA t1[t1$Petal.Width ==
> > > >> 2.0, ]
> > > > Sepal.Length Sepal.Width Petal.Length Petal.Width Species
> > > > NA NA NA NA NA <NA>
> > > > NA.1 NA NA NA NA <NA>
> > > > NA.2 NA NA NA NA <NA>
> > > > NA.3 NA NA NA NA <NA>
> > > > 111 6.5 3.2 5.1 2 virginica
> > > > 114 5.7 2.5 5.0 2 virginica
> > > > NA.4 NA NA NA NA <NA>
> > > > 122 5.6 2.8 4.9 2 virginica
> > > > 123 7.7 2.8 6.7 2 virginica
> > > > NA.5 NA NA NA NA <NA>
> > > > NA.6 NA NA NA NA <NA>
> > > > NA.7 NA NA NA NA <NA>
> > > > NA.8 NA NA NA NA <NA>
> > > > 132 7.9 3.8 6.4 2 virginica
> > > > NA.9 NA NA NA NA <NA>
> > > > NA.10 NA NA NA NA <NA>
> > > > 148 6.5 3.0 5.2 2 virginica
> > > > NA.11 NA NA NA NA <NA>
> > > >
> > > > ## Twelve values were replaced, twelve NA rows appeared.
> > > >
> > > > ### MISC INFO ###
> > > >> sessionInfo()
> > > > R version 3.4.0 (2017-04-21)
> > > > Platform: x86_64-apple-darwin16.5.0 (64-bit) Running under: macOS
> > > > 10.14.2
> > > >
> > > > Matrix products: default
> > > > BLAS:
> > > > /System/Library/Frameworks/Accelerate.framework/Versions/A/Framewo
> > > > rks/ vecLib.framework/Versions/A/libBLAS.dylib
> > > > LAPACK:
> > > > /System/Library/Frameworks/Accelerate.framework/Versions/A/Framewo
> > > > rks/ vecLib.framework/Versions/A/libLAPACK.dylib
> > > >
> > > > locale:
> > > > [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
> > > >
> > > > attached base packages:
> > > > [1] stats graphics grDevices utils datasets methods base
> > > >
> > > > loaded via a namespace (and not attached):
> > > > [1] compiler_3.4.0 tools_3.4.0
> > > >> Sys.getlocale()
> > > > [1] "en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-
> 8"
> > > >
> > > >
> > > > Thank you,
> > > > Ernest
> > > >
> > > > ______________________________________________
> > > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > > PLEASE do read the posting guide
> > > > http://www.R-project.org/posting-guide.html
> > > > and provide commented, minimal, self-contained, reproducible code.
> > > >
> > >
> > > ______________________________________________
> > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > > https://stat.ethz.ch/mailman/listinfo/r-help
> > > PLEASE do read the posting guide
> > > http://www.R-project.org/posting-guide.html
> > > and provide commented, minimal, self-contained, reproducible code.
> > Osobní údaje: Informace o zpracování a ochraně osobních údajů
> > obchodních partnerů PRECHEZA a.s. jsou zveřejněny na:
> > https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information
> > about processing and protection of business partner’s personal data
> > are available on website:
> > https://www.precheza.cz/en/personal-data-protection-principles/
> > Důvěrnost: Tento e-mail a jakékoliv k němu připojené dokumenty jsou
> > důvěrné a podléhají tomuto právně závaznému prohláąení o vyloučení
> > odpovědnosti: https://www.precheza.cz/01-dovetek/ | This email and any
> > documents attached to it may be confidential and are subject to the
> > legally binding disclaimer: https://www.precheza.cz/en/01-disclaimer/
> >
Osobní údaje: Informace o zpracování a ochraně osobních údajů obchodních
partnerů PRECHEZA a.s. jsou zveřejněny na:
https://www.precheza.cz/zasady-ochrany-osobnich-udaju/ | Information about
processing and protection of business partner’s personal data are available on
website: https://www.precheza.cz/en/personal-data-protection-principles/
Důvěrnost: Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a
podléhají tomuto právně závaznému prohláąení o vyloučení odpovědnosti:
https://www.precheza.cz/01-dovetek/ | This email and any documents attached to
it may be confidential and are subject to the legally binding disclaimer:
https://www.precheza.cz/en/01-disclaimer/
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
