[R] Apply functions along layers of a data matrix
Hello
How can I apply functions along layers of a data matrix?
Example:
daf - data.frame(
'id' = rep(1:5, 3),
matrix(1:60, nrow=15, dimnames=list( NULL, paste('v', 1:4, sep='') )),
rep = rep(1:3, each=5)
)
The data frame daf contains 3 repetitions/layers (rep) of 4 variables
of 5 persons (id). For some reason, I want to calculate various
statistics (e.g., mean, median) *along* the repetitions. The mean
calculation, for example, would produce the means of daf[1, 'v1']
*along* the 3 repetition:
(daf[1, 'v1'] + daf[6, 'v1'] + daf[11, 'v1']) / 3
That is to say, each of the calculations would result in a data frame
with 4 variables (and the id) of the 5 persons:
id v1 v2 v3 v4
1 1 6 21 36 51
2 2 7 22 37 52
3 3 8 23 38 53
4 4 9 24 39 54
5 5 10 25 40 55
Currently, I do this in a loop, but I was wondering about a quick and
ressource-friendly way to achieve this?
Thanks
*S*
--
Sascha Vieweg, saschav...@gmail.com
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Re: [R] Apply functions along layers of a data matrix
Hi:
Here are two ways to do it; further solutions can be found in the doBy
and data.table packages, among others.
library('plyr')
ddply(daf, .(id), colwise(mean, c('v1', 'v2', 'v3', 'v4')))
aggregate(cbind(v1, v2, v3, v4) ~ id, data = daf, FUN = mean)
# Result of each:
id v1 v2 v3 v4
1 1 6 21 36 51
2 2 7 22 37 52
3 3 8 23 38 53
4 4 9 24 39 54
5 5 10 25 40 55
Dennis
On Fri, Nov 18, 2011 at 5:05 AM, saschav...@gmail.com wrote:
Hello
How can I apply functions along layers of a data matrix?
Example:
daf - data.frame(
'id' = rep(1:5, 3),
matrix(1:60, nrow=15, dimnames=list( NULL, paste('v', 1:4, sep='') )),
rep = rep(1:3, each=5)
)
The data frame daf contains 3 repetitions/layers (rep) of 4 variables of 5
persons (id). For some reason, I want to calculate various statistics (e.g.,
mean, median) *along* the repetitions. The mean calculation, for example,
would produce the means of daf[1, 'v1'] *along* the 3 repetition:
(daf[1, 'v1'] + daf[6, 'v1'] + daf[11, 'v1']) / 3
That is to say, each of the calculations would result in a data frame with 4
variables (and the id) of the 5 persons:
id v1 v2 v3 v4
1 1 6 21 36 51
2 2 7 22 37 52
3 3 8 23 38 53
4 4 9 24 39 54
5 5 10 25 40 55
Currently, I do this in a loop, but I was wondering about a quick and
ressource-friendly way to achieve this?
Thanks
*S*
--
Sascha Vieweg, saschav...@gmail.com
__
R-help@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.
__
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and provide commented, minimal, self-contained, reproducible code.
Re: [R] Apply functions along layers of a data matrix
On 11/18/2011 01:05 PM, saschav...@gmail.com wrote:
daf - data.frame(
'id' = rep(1:5, 3),
matrix(1:60, nrow=15, dimnames=list( NULL, paste('v', 1:4, sep='') )),
rep = rep(1:3, each=5)
)
Hi,
This seems like a job for plyr!
library(plyr)
ddply(daf, .(rep), summarise, mn = mean(v1))
hope this helps,
Paul
--
Paul Hiemstra, Ph.D.
Global Climate Division
Royal Netherlands Meteorological Institute (KNMI)
Wilhelminalaan 10 | 3732 GK | De Bilt | Kamer B 3.39
P.O. Box 201 | 3730 AE | De Bilt
tel: +31 30 2206 494
http://intamap.geo.uu.nl/~paul
http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770
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and provide commented, minimal, self-contained, reproducible code.
Re: [R] Apply functions along layers of a data matrix
On Nov 18, 2011, at 8:05 AM, saschav...@gmail.com wrote:
Hello
How can I apply functions along layers of a data matrix?
Example:
daf - data.frame(
'id' = rep(1:5, 3),
matrix(1:60, nrow=15, dimnames=list( NULL, paste('v', 1:4,
sep='') )),
rep = rep(1:3, each=5)
)
The data frame daf contains 3 repetitions/layers (rep) of 4
variables of 5 persons (id). For some reason, I want to calculate
various statistics (e.g., mean, median) *along* the repetitions. The
mean calculation, for example, would produce the means of daf[1,
'v1'] *along* the 3 repetition:
(daf[1, 'v1'] + daf[6, 'v1'] + daf[11, 'v1']) / 3
That is to say, each of the calculations would result in a data
frame with 4 variables (and the id) of the 5 persons:
id v1 v2 v3 v4
1 1 6 21 36 51
2 2 7 22 37 52
3 3 8 23 38 53
4 4 9 24 39 54
5 5 10 25 40 55
I see you have gotten acouple of plyr solutions but this is really
easy in base R:
aggregate(daf[-c(1,6)], list(daf$id), mean)
Group.1 v1 v2 v3 v4
1 1 6 21 36 51
2 2 7 22 37 52
3 3 8 23 38 53
4 4 9 24 39 54
5 5 10 25 40 55
You read this as use the mean function within categories defined by
the id INDEX to aggregate the columns except tof the first and 6th
columns
Currently, I do this in a loop, but I was wondering about a quick
and ressource-friendly way to achieve this?
Thanks
*S*
--
Sascha Vieweg, saschav...@gmail.com
__
R-help@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.
David Winsemius, MD
West Hartford, CT
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and provide commented, minimal, self-contained, reproducible code.
