[R] Conditional operations in R

[R. Michael Weylandt]

On Tue, Sep 18, 2012 at 3:41 PM, ramoss <ramine.mossadegh at finra.org> wrote:
> Hello,
>
> I am a newbie to R coming from SAS background. I am trying to program the
> following:
> I have a monthly data frame with 2 variables:
>
> client   pct_total
> A          15%
> B          10%
> C          10%
> D          9%
> E           8%
> F          6%
> G          4%
>
> I need to come up w/ a monthly list of clients that make 50% or just above
> it every month so I can pass them to the rest of the program.  In this case
> the list would contain the first 4 rows.
> top <- client[c(1,4),]
> toptot <- sum(top$PCTTOT)
> How can I make this automatic?  In SAS I would use macro w/ a do while.
> Thanks for your help.
>

If I understand the algorithm correctly, you take a cumulative sum of
the pct_total column and want the index of the first place that passes
50%:

try

with(DATA, which.max(cumsum(pct_total) > 0.5))

which is admittedly rather opaque.

Also in: top <- client[c(1,4),]

That's not rows 1 to 4 but rows one and 4: you need instead: seq(1,4)
to make c(1,2,3,4).

Cheers,
Michael


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