[R] tapply

[Weiwei Shi]

Even before I tried, I already realize it must be true when I read
this reply! Great job! thanks, Andy.

> str(z)
`data.frame':   235 obs. of  2 variables:
 $ CLAIMNUM : Factor w/ 1907 levels "0","10000001849",..: 1083 1083
1083 1582 1582 1084 1681 1681 1391 1391 ...
 $ SIU.SAVED: int  475 3000 3000 0 0 4352 0 0 4500 3000 ...

So, I have another general question: how to avoid this when I do the matching?
In my case, claimnum does not have to be a factor.  I think I can do
as.integer on it to de-factor it. But, I want to know how to do it w/
keeping is as factor? btw, what's your way to drop those levels?  :)

weiwei 


On 6/21/05, Liaw, Andy <andy_liaw at merck.com> wrote:
> What does str(z) say?  I suspect the second column is a factor, which, after
> the subsetting, has some empty levels.  If so, just drop those levels.
> 
> Andy
> 
> > From: Weiwei Shi
> >
> > hi
> > i tried all the methods suggested above:
> > ave and rowsum with "with" function works for my situation. I think
> > the problem might not be due to tapply.
> > My data z comes from
> > z<-y[y[[1]] %in% x[[2]], c(1,9)]
> >
> > while z is supposed to have no entries for those non-matched
> > between x and y.
> >
> > however, when I run tapply, and the result also includes those
> > non-matched entries. I use is.na function to remove those entry from z
> > first and then use tapply again, but the result is the same: those
> > NA's and those non-matched results are still there. That's what I mean
> > by "it doesn't work".
> >
> > Is there something I missed here so that z "implicitly" has some
> > "trace" back to y dataset?
> >
> > thanks,
> >
> > On 6/20/05, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > > On 6/20/05, Weiwei Shi <helprhelp at gmail.com> wrote:
> > > > hi,
> > > > i have another question on tapply:
> > > > i have a dataset z like this:
> > > > 5540 389100307391      2600
> > > > 5541 389100307391      2600
> > > > 5542 389100307391      2600
> > > > 5543 389100307391      2600
> > > > 5544 389100307391      2600
> > > > 5546 381300302513        NA
> > > > 5547 387000307470        NA
> > > > 5548 387000307470        NA
> > > > 5549 387000307470        NA
> > > > 5550 387000307470        NA
> > > > 5551 387000307470        NA
> > > > 5552 387000307470        NA
> > > >
> > > > I want to sum the column 3 by column 2.
> > > > I removed NA by calling:
> > > > tapply(z[[3]], z[[2]], sum, na.rm=T)
> > > > but it does not work.
> > > >
> > > > then, i used
> > > > z1<-z[!is.na(z[[3]],]
> > > > and repeat
> > > > still doesn't work.
> > > >
> > > > please help.
> > > >
> > >
> > > Depending on what you want you may be able to use rowsum:
> > >
> > > - display only groups that have at least one non-NA with the sum
> > >   being the sum of the non-NAs:
> > >
> > >         with(na.omit(z), rowsum(V3, V2))
> > >
> > > - display all groups with the sum being NA if any member is NA:
> > >
> > >         rowsum(z$V3, z$V2)
> > >
> >
> >
> > --
> > Weiwei Shi, Ph.D
> >
> > "Did you always know?"
> > "No, I did not. But I believed..."
> > ---Matrix III
> >
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> >
> >
> >
> 
> 
> 
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