> Re: [R] Counting Elements Conditionally
> Jean V Adams
> to:
> Edward Patzelt
> 08/22/2011 03:53 PM
>
> > [R] Counting Elements Conditionally
> > Edward Patzelt
> > to:
> > r-help
> > 08/22/2011 02:33 PM
> >
> > R -
> >
> > I have 3 variables with data below. Variable "Rev" is a vector that
> changes
> > from 1 to 2, 2 to 3, etc.... Variable "FF" is a binary variable with
> 1's
> > and 0's. Variable "bin" is a different binary variable with 1's and
> 0's.
> >
> > I want to calculate the number of elements:
> >
> > 1. Starting with the first element where Rev switches (i.e. 1 to 2)
> >
> > 2. The number of elements between the transition and the first 0 in
the
> > "FF" vector; *when "bin" is also a 0.*
> > *
> > *
> > 3. I want to do this for each transition in Rev, but ignore all
> elements
> > after calculating #2 until another transition has occurred.
> >
> >
> > structure(list(Rev = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
> > 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L,
> > 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), FF = c(0L,
> > 1L, 1L, 1L, 1L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 1L, 1L,
> > 1L, 1L, 0L, 1L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 0L, 0L, 1L, 1L,
> > 1L, 1L, 1L, 0L, 1L, 1L, 1L), bin = c(NA, 1, 1, 1, 1, 1, 1, 1,
> > 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
> > 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 1)), .Names = c("Rev", "FF", "bin"
> > ), row.names = c(NA, -40L), class = "data.frame")
> >
> >
> > --
> > Edward H. Patzelt
> > Research Assistant ? TRiCAM Lab
> > University of Minnesota ? Psychology/Psychiatry
> > VA Medical Center
> > Office: S355 Elliot Hall - Twin Cities Campus
> > Phone: 612-626-0072 Email: patze...@umn.edu
> >
>
> Try this (I'm assuming your data.frame is called "df":
>
>
> uR <- unique(df$Rev)
> uR0 <- uR*10L
>
> first.Rev <- match(uR, df$Rev)
> first.Rev0 <- match(uR0, df$Rev * 10L + df$FF)
>
> no.elements <- first.Rev0 - first.Rev + 1
>
>
> This starts with Rev=1 (rather than Rev=2), but you can get rid of that
by
> dropping the first result ...
>
>
> no.elements[-1]
>
>
> Jean
>
Ooops. Too hasty in my reply. I missed the part about bin also being
zero. Try this instead.
uR <- unique(df$Rev)
uR00 <- uR*100L
first.Rev <- match(uR, df$Rev)
first.Rev00 <- match(uR00, df$Rev * 100L + df$FF * 10L + df$bin)
no.elements <- first.Rev00 - first.Rev + 1
Jean
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