[R] A. Mani : Avoiding loops

[Petr Pikal]

Hi

Or maybe table

> mat<-matrix(sample(LETTERS[1:4], 200, replace=T),40,5)
> df<-data.frame(mat)
> table(df$X4)

 A  B  C  D 
 8 12 11  9 
>

is what is wanted

HTH
Petr



On 19 Aug 2005 at 7:24, Sean O'Riordain wrote:

> Hi,
> I'm not sure what you actually want from your email (following the
> posting guide is a good way of helping you explain things to the rest
> of us in a way we understand - it might even answer your question!
> 
> I'm only a beginner at R so no doubt one of our expert colleagues will
> help me...
> 
> > fred <- data.frame()
> > fred <- edit(fred)
> > fred
>   A B C D E
> 1 1 2 X Y 1
> 2 2 3 G L 1
> 3 3 1 G L 5
> > fred[,3]
> [1] X G G
> Levels: G X
> > fred[fred[,3]=="G",]
>   A B C D E
> 2 2 3 G L 1
> 3 3 1 G L 5
> 
> so at this point I can create a new dataframe with column 3 (C) ==
> "G"; either explicitly or implicitly...
> 
> and if I want to calculate the sum() of column E, then I just say
> something like...
> 
> > sum(fred[fred[,3]=="G",][,5])
> [1] 6
> >
> 
> now naturally being a bit clueless at manipulating stuff in R, I
> didn't know how to do this before I started... and you guys only get
> to see the lines that I typed in and got a "successful" result...
> 
> according to section 6 of the "Introduction to R" manual which comes
> with R, I could also have said > sum(fred[fred$C=="G",]$E) [1] 6
> 
> Hmmm.... I wonder would it be reasonable to put an example of this
> type into section 2.7 of the "Introduction to R"?
> 
> 
> cheers!
> Sean
> 
> 
> On 18/08/05, A. Mani <a_mani_sc_gs at vsnl.net> wrote:
> > Hello,
> >         I want to avoid loops in the following situation. There is a
> >         5-col
> > dataframe with col headers alone. two of the columns are
> > non-numeric. The problem is to calculate statistics(scores) for each
> > element of one column. The functions depend on matching in the other
> > non-numeric column.
> > 
> > A  B  C  E  F
> > 1  2  X  Y  1
> > 2  3  G  L  1
> > 3  1  G  L  5
> > and so on ...30000+ entries.
> > 
> > I need scores for col E entries which depend on conditional
> > implications.
> > 
> > 
> > Thanks,
> > 
> > A. Mani
> > Member, Cal. Math. Soc
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
> >
> 
> ______________________________________________
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Petr Pikal
petr.pikal at precheza.cz