On Nov 15, 2011, at 6:46 AM, R. Michael Weylandt wrote:
Good morning Rob,
First off, thank you for providing a reproducible example. This is one
of those little tasks that R is pretty great at, but there exist
\infty ways to do so and it can be a little overwhelming for the
beginner: here's one with the base function ave():
cbind(ave(example[,2:4], example[,5]), id = example[,5])
This splits example according to the fifth column (id) and averages
the other values: we then stick another copy of the id back on the end
and are good to go.
The base function aggregate can do something similar:
aggregate(example[,2:4], by = example[,5, drop = F], mean)
Note that you need the little-publicized but super useful drop = F
command to make this one work.
The way I usually deal with that is to wrap list() around the by=
argument ... since I usually forget about this aggregate quirk and
bet an error message complaining : "'by' must be a list". (drop=FALSE
has the effect of keeping data.frame columns as lists too, so I am not
disagreeing here.)
aggregate(example[,2:4], by = list(example[,5]), mean)
--
David.
There are other ways to do this with the plyr or doBy packages as
well, but this should get you started.
Hope it helps,
Michael
On Tue, Nov 15, 2011 at 5:52 AM, robgriffin247
<robgriffin...@hotmail.com> wrote:
*The situation (or an example at least!)*
example<-data.frame(rep(letters[1:10]))
colnames(example)[1]<-("Letters")
example$numb1<-rnorm(10,1,1)
example$numb2<-rnorm(10,1,1)
example$numb3<-rnorm(10,1,1)
example$id<-
c
("CG234
","CG232
","CG441","CG128","CG125","CG182","CG232","CG441","CG232","CG125")
*this produces something like this:*
Letters numb1 numb2 numb3 id
1 a 0.8139130 -0.9775570 -0.002996244 CG234
2 b 0.8268700 0.4980661 1.647717998 CG232
3 c 0.2384088 1.0249684 0.120663273 CG441
4 d 0.8215922 0.5686534 1.591208307 CG128
5 e 0.7865918 0.5411476 0.838300185 CG125
6 f 2.2385522 1.2668070 1.268005020 CG182
7 g 0.7403965 -0.6224205 1.374641549 CG232
8 h 0.2526634 1.0282978 -0.110449844 CG441
9 i 1.9333444 1.6667486 2.937252363 CG232
10 j 1.6996701 0.5964623 1.967870617 CG125
*The Problem:*
Some of these id's are repeated, I want to average the values for
those rows
within each column but obviously they have different numbers in the
numbers
column, and they also have different letters in the letters column,
the
letters are not necessary for my analysis, only the duplicated id's
and the
numb columns are important
I also need to keep the existing dataframe so would like to build a
new
dataframe that averages the repeated values and keeps their id - my
actual
dataset is much more complex (271*13890) - but the solution to this
can be
expanded out to my main data set because there is just more columns
of
numbers and still only one alphanumeric id to keep in my example
data, id
CG232 occurs 3 times, CG441 & CG125 occur twice, everthing else
once so the
new dataframe (from this example) there would be 3 number columns
(numb1,
numb2, numb3) and an id the numb column values would be the
averages of the
rows which had the same id
so for example the new dataframe would contain an entry for CG125
which
would be something like this:
numb1 numb2 numb3 id
1.2431 0.5688 1.403 CG125
Just as a thought, all of the IDs start with CG so could I use then
grep (?)
to delete CG and replace it with 0, that way duplicated ids could be
averaged as a number (they would be the same) but I still don’t
know how to
produce the new dataframe with the averaged rows in it...
I hope this is clear enough! email me if you need further detail or
even
better, if you have a solution!!
also sorry to be posting my second question in under 24hours but I
seem to
have become more than a little stuck – I was making such good
progress with
R!
Rob
(also I'm sorry if this appears more than once on the mailing list
- I'm
having some network & windows live issues so I'm not convinced
previous
attempts to send this have worked, but have no way of telling if
they are
just milling around in the internet somewhere as we speak and will
decide to
come out of hiding later!)
--
View this message in context:
http://r.789695.n4.nabble.com/averaging-between-rows-with-repeated-data-tp4042513p4042513.html
Sent from the R help mailing list archive at Nabble.com.
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______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
