I'd like to get a long data set of minimum values from groups in another
data
set.
The following almost does what I want. (Note, I'm using the word factor
differently from it's meaning in R; bad choice of words)
myframe = data.frame(factor1 = rep(1:2,each=8), factor2
rep(c("a","b"),each=4, times=2), factor3 =
rep(c("x","y"),each=2, times=4),
y=1:16)
attach(myframe)
minimums = by(y, list(factor1, factor2,factor3), min)
detach(myframe)
The problem is that "minimums" is object of class "by",
which looks like
some kind of array with the number of dimension equal to the number of
factors. I just want two dimensions though, with factors in columns. I can't
figure out how to reformat it to something like this:
factor1 factor2 factor2 y
1 a x 1
2 a x 9
1 b x 5
...
I could make nested for loops, but I'd like something that will work for an
arbitrary number of factors. I've seen some functions that will rearrange
data (e.g. reshape), but they all seem to require a data.frame to start
with.
--
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Sent from the R help mailing list archive at Nabble.com.
On Jan 11, 2010, at 7:58 PM, JustinNabble wrote:> > I'd like to get a long data set of minimum values from groups in > another data > set. > The following almost does what I want. (Note, I'm using the word > factor > differently from it's meaning in R; bad choice of words) > > myframe = data.frame(factor1 = rep(1:2,each=8), factor2 > rep(c("a","b"),each=4, times=2), factor3 = rep(c("x","y"),each=2, > times=4), > y=1:16) > attach(myframe)# with(myframe, ....) would be a better construction> minimums = by(y, list(factor1, factor2,factor3), min) > detach(myframe)It's a table, which IS like an array, You want: > as.data.frame.table(minimums) Var1 Var2 Var3 Freq 1 1 a x 1 2 2 a x 9 3 1 b x 5 4 2 b x 13 5 1 a y 3 6 2 a y 11 7 1 b y 7 8 2 b y 15> > The problem is that "minimums" is object of class "by", which looks > like > some kind of array with the number of dimension equal to the number of > factors. I just want two dimensions though, with factors in columns. > I can't > figure out how to reformat it to something like this: > > factor1 factor2 factor2 y > 1 a x 1 > 2 a x 9 > 1 b x 5 > ... > > I could make nested for loops, but I'd like something that will work > for an > arbitrary number of factors. I've seen some functions that will > rearrange > data (e.g. reshape), but they all seem to require a data.frame to > start > with. > ---- David Winsemius, MD Heritage Laboratories West Hartford, CT
Tena koe Justin Try aggregate(): e.g., aggregate(myframe[,4], myframe[,1:3], min) HTH .... Peter Alspach> -----Original Message----- > From: r-help-bounces at r-project.org > [mailto:r-help-bounces at r-project.org] On Behalf Of JustinNabble > Sent: Tuesday, 12 January 2010 1:58 p.m. > To: r-help at r-project.org > Subject: [R] How to get minimum value by group > > > I'd like to get a long data set of minimum values from groups > in another data set. > The following almost does what I want. (Note, I'm using the > word factor differently from it's meaning in R; bad choice of words) > > myframe = data.frame(factor1 = rep(1:2,each=8), factor2 = > rep(c("a","b"),each=4, times=2), factor3 = > rep(c("x","y"),each=2, times=4), > y=1:16) > attach(myframe) > minimums = by(y, list(factor1, factor2,factor3), min) > detach(myframe) > > The problem is that "minimums" is object of class "by", which > looks like some kind of array with the number of dimension > equal to the number of factors. I just want two dimensions > though, with factors in columns. I can't figure out how to > reformat it to something like this: > > factor1 factor2 factor2 y > 1 a x 1 > 2 a x 9 > 1 b x 5 > ... > > I could make nested for loops, but I'd like something that > will work for an arbitrary number of factors. I've seen some > functions that will rearrange data (e.g. reshape), but they > all seem to require a data.frame to start with. > -- > View this message in context: > http://n4.nabble.com/How-to-get-minimum-value-by-group-tp10117 > 45p1011745.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org 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. >
Try this:> aggregate(myframe[4], myframe[1:3], min)factor1 factor2 factor3 y 1 1 a x 1 2 2 a x 9 3 1 b x 5 4 2 b x 13 5 1 a y 3 6 2 a y 11 7 1 b y 7 8 2 b y 15 On Mon, Jan 11, 2010 at 7:58 PM, JustinNabble <justinmmcgrath at hotmail.com> wrote:> > I'd like to get a long data set of minimum values from groups in another data > set. > The following almost does what I want. (Note, I'm using the word factor > differently from it's meaning in R; bad choice of words) > > myframe = data.frame(factor1 = rep(1:2,each=8), factor2 > rep(c("a","b"),each=4, times=2), factor3 = rep(c("x","y"),each=2, times=4), > y=1:16) > attach(myframe) > minimums = by(y, list(factor1, factor2,factor3), min) > detach(myframe) > > The problem is that "minimums" is object of class "by", which looks like > some kind of array with the number of dimension equal to the number of > factors. I just want two dimensions though, with factors in columns. I can't > figure out how to reformat it to something like this: > > factor1 factor2 factor2 y > 1 ? ? ? ? a ? ? ? ? x ? ? ? ? 1 > 2 ? ? ? ? a ? ? ? ? x ? ? ? ? 9 > 1 ? ? ? ? b ? ? ? ? x ? ? ? ? 5 > ... > > I could make nested for loops, but I'd like something that will work for an > arbitrary number of factors. I've seen some functions that will rearrange > data (e.g. reshape), but they all seem to require a data.frame to start > with. > -- > View this message in context: http://n4.nabble.com/How-to-get-minimum-value-by-group-tp1011745p1011745.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org 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. >