[R] A. Mani : Avoiding loops

[Sean O'Riordain]

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
> 
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