[R] na.omit - Is it working properly?

[Andrew Robinson]

Hi Sarah,

I'm not sure that I understand your problem.  You have shown us three
ways to try to omit missing values, and one of them seems to work.
But you're concerned because some aspect of it doesn't match the ones
that don't work?  But they don't work!  

I wonder if you could send an example in commented, minimal,
self-contained, reproducible code ...

Cheers

Andrew

On Tue, May 03, 2011 at 12:18:03PM -0700, Kalicin, Sarah wrote:
> 
> I have a work around for this, but can someone explain why the first example does not work properly? I believed it worked in the previous version of R, by selecting just the rows=200525 and omitting the na's. I just upgraded to 2.13. I am also concern with the row numbers being different in the selections, should I be worried? FYI, I just selected the first few rows for demonstration, please do not worry that the number of rows shown are not equal. - Sarah
> 
> With na.omit around the column, but it is showing other values in the F.WW column other than 200525, along with NA.  I was hoping that this would omit all the NA's, and show all the rows that P$F.WW=200525. I believe it did with the previous version of R.
> P[na.omit(P$F.WW)==200525, c(51, 52)]
>           F.WW        R.WW
> 45      200525          NA
> 53          NA          NA
> 61      200534      200534
> 63      200608      200608
> 66      200522      200541
> 80          NA          NA
> 150     200521      200516
> 231     200530      200530
> 
> No na.omit, the F.WW=200525 seems to work, but lots of NA included. This is what is expected!! The row numbers are not the same as the above example, except the first row.
> > P[P$F.WW==200525, c(51, 52)]
>             F.WW     R.WW
> 45        200525          NA
> NA            NA          NA
> NA.1          NA          NA
> NA.2          NA          NA
> NA.3          NA          NA
> 57        200525      200526
> 65        200525          NA
> 67        200525          NA
> 70        200525      200525
> NA.4          NA          NA
> NA.5          NA          NA
> 86        200525          NA
> 
> Na.omit excludes the na's. This is what I want. The concern I have is why the row numbers do not match any of those shown in the examples above.
> > na.omit(P[P$F.WW==200525, c(51, 52)])
>         F.WW        R.WW
> 57    200525      200526
> 70    200525      200525
> 161   200525      200525
> 245   200525      200525
> 246   200525      200525
> 247   200525      200526
> 256   200525      200525
> 266   200525      200525
> 269   200525      200525
> 271   200525      200526
> 276   200525      200526
> 278   200525      200526
> 
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> 
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-- 
Andrew Robinson  
Program Manager, ACERA 
Department of Mathematics and Statistics            Tel: +61-3-8344-6410
University of Melbourne, VIC 3010 Australia               (prefer email)
http://www.ms.unimelb.edu.au/~andrewpr              Fax: +61-3-8344-4599
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