[R] Help on manipulating a data frame

[Gabor Grothendieck]

Just change f appropriately, e.g.

f <- function(x) {
	v <- embed(x$Sign, 4) %*% c(0, 1, -1, 1) == 3
	if (any(v)) x[which.max(v) + 3, ]
}

On 4/23/07, Alfonso Sammassimo <cincinattikid at bigpond.com> wrote:
> Thankyou for your reply Gabor.
>
>
>
> Your code helped me get started in creating id for each week of month. What
> I'm really looking for though is a more general application where I can
> extract each final week of the month conditional on the pattern of values
> (simply plus or minus signs) of the weeks preceding it in that month (i
> didnt really explain that in my previous post).
>
> For example, with the data below:
>
>
>
>                    Date              Value         Sign Week
>
> 2005-02.4   2005-02-04  1.67427972    1    1
>
> 2005-02.5   2005-02-11  0.00000000    0    2
>
> 2005-02.6   2005-02-18  0.14221382    1    3
>
> 2005-02.7   2005-02-25 -0.85633254   -1    4
>
> 2005-03.8   2005-03-04  2.22073856    1    1
>
> 2005-03.9   2005-03-11 -0.07011803   -1    2
>
> 2005-03.10  2005-03-18  1.00035730    1    3
>
> 2005-03.11  2005-03-25 -2.48430869   -1    4
>
> 2005-04.12  2005-04-01 -0.04747211   -1    1
>
> 2005-04.13  2005-04-08  0.18975338    1    2
>
> 2005-04.14  2005-04-15 -3.54552994   -1    3
>
> 2005-04.15  2005-04-22  0.51426586    1    4
>
> 2005-04.16  2005-04-29 -1.52599565   -1    5
>
>
>
> if I wanted to show the last week of any months where the pattern of the
> signs of the three  preceding weeks was "1,-1,1" , then the following would
> be returned:
>
>
>
>                     Date              Value          Sign  Week
>
> 2005-03.11  2005-03-25 -2.48430869   -1      4
>
> 2005-04.16  2005-04-29 -1.52599565   -1      5
>
>
>
> I would greatly appreciate any hint or example which might lead me the right
> way on this.
>
>
>
> Thankyou,
>
>
>
> Alf Sammassimo
>
> ----- Original Message -----
> From: "Gabor Grothendieck" <ggrothendieck at gmail.com>
> To: "Alfonso Sammassimo" <cincinattikid at bigpond.com>
> Cc: <r-help at stat.math.ethz.ch>
> Sent: Monday, April 23, 2007 2:31 PM
> Subject: Re: [R] Help on manipulating a data frame
>
>
> > Do you mean you want to return the first row for each mont for
> > which the value > 0?
> >
> > In that case try this.  The first group of lines recreates your
> > data frame and calls it DF.  by causes f to operate on a subset of
> > rows comprising one month extracting the first row for which
> > the value is positive and also adding in the week number.
> > do.call rbinds the results from each month altogether.
> >
> > Input <- "2007-01-05 -1.52377151
> > 2007-01-12  1.04787390
> > 2007-01-19  0.61647047
> > 2007-01-26  1.87864283
> > 2007-02-02  0.54992405
> > 2007-02-09  1.96850069
> > 2007-02-16  0.26850159
> > 2007-02-23  1.56305144
> > 2007-03-02 -4.19500573
> > 2007-03-09  0.77127814
> > 2007-03-16  0.32387312
> > 2007-03-23  2.02163219
> > 2007-03-30  0.63175605
> > 2007-04-06  1.33346284
> > 2007-04-13  0.96021569"
> > DF <- read.table(textConnection(Input), col.names = c("Date", "Value"),
> > colClasses = c("Date", "numeric"))
> >
> > f <- function(x) cbind(x, Week = seq_len(nrow(x)))[which.max(x$Value >
> > 0),]
> > do.call("rbind", by(DF, format(DF$Date, "%Y-%m"), f))
> >
> > On 4/22/07, Alfonso Sammassimo <cincinattikid at bigpond.com> wrote:
> >> Hi R-experts,
> >>
> >>
> >>
> >> I have a large set of weekly data in this format:
> >>
> >>
> >>
> >> 2007-01-05 -1.52377151
> >> 2007-01-12  1.04787390
> >> 2007-01-19  0.61647047
> >> 2007-01-26  1.87864283
> >> 2007-02-02  0.54992405
> >> 2007-02-09  1.96850069
> >> 2007-02-16  0.26850159
> >> 2007-02-23  1.56305144
> >> 2007-03-02 -4.19500573
> >> 2007-03-09  0.77127814
> >> 2007-03-16  0.32387312
> >> 2007-03-23  2.02163219
> >> 2007-03-30  0.63175605
> >> 2007-04-06  1.33346284
> >> 2007-04-13  0.96021569
> >>
> >>
> >>
> >> How might this data be sorted to something like this?:
> >>
> >>
> >>
> >> Date               Week of Month     Value
> >>
> >> 2007-01-05          1                     -1.52377151
> >> 2007-01-12          2                      1.04787390
> >> 2007-01-19          3                      0.61647047
> >> 2007-01-26          4                      1.87864283
> >>
> >> 2007-02-02          1                      0.54992405
> >>
> >>
> >>
> >> My aim is to return the last value of every month where the previous
> >> values
> >> in that month were negative values, hence the need to split the data by
> >> month. Any guide as to how this might this be possible without a loop?
> >>
> >>
> >>
> >> Any help would be much appreciated.
> >>
> >>
> >>
> >> Thanks,
> >>
> >>
> >>
> >> Alf Sammassimo
> >>
> >> Melbourne, Australia
> >>
> >> ______________________________________________
> >> 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
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
>
>
>