remove rows in data frame by average
On Feb 21, 2013, at 2:15 PM, William Dunlap wrote:
Many find the functions in the plyr package more convenient to use than the do.call(rbind, lapply(split(...),...) business:
library(plyr) ddply(dat1, .(Subject,Block), summarize, MeanFeature1=mean(Feature1), MeanFeature2=mean(Feature2))
Subject Block MeanFeature1 MeanFeature2 1 1 1 55.0 29.0 2 1 2 42.5 38.5 3 1 3 64.0 14.0 Change the calls to 'mean' to calls to other summary functions like 'sum' or 'max' as you wish.
Apropos something less complex than "the do.call( lapply( split...)) business": The same sort of operation is provided by `aggregate` when the function to be applied on all columns is the same:
aggregate(dat1[, c('Feature1', 'Feature2')] , dat1[, c("Subject", "Block")], FUN=mean)
Subject Block Feature1 Feature2 1 1 1 55.0 29.0 2 1 2 42.5 38.5 3 1 3 64.0 14.0
David > Bill Dunlap > Spotfire, TIBCO Software > wdunlap tibco.com > > >> -----Original Message----- >> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf >> Of arun >> Sent: Thursday, February 21, 2013 1:45 PM >> To: Johannes Brand >> Cc: R help >> Subject: Re: [R] remove rows in data frame by average >> >> Hi, >> >> May be this helps: >> >> dat1<- read.table(text=" >> Subject Block Trial Feature1 Feature2 >> 1 1 1 48 40 >> 1 1 2 62 18 >> 1 2 1 34 43 >> 1 2 2 51 34 >> 1 3 1 64 14 >> ",sep="",header=TRUE) >> >> >> res1<-do.call(rbind,lapply(split(dat1,dat1$Block),function(x) >> data.frame(unique(x[,1:2]),t(colMeans(x[,-c(1:3)]))))) >> res1 >> # Subject Block Feature1 Feature2 >> #1 1 1 55.0 29.0 >> #2 1 2 42.5 38.5 >> #3 1 3 64.0 14.0 >> >> >> #With multiple subjects: >> dat2<- read.table(text=" >> Subject Block Trial Feature1 Feature2 >> 1 1 1 48 40 >> 1 1 2 62 18 >> 1 2 1 34 43 >> 1 2 2 51 34 >> 1 3 1 64 14 >> 2 1 1 48 35 >> 2 1 2 54 15 >> 2 2 1 49 50 >> 2 2 2 64 40 >> 2 3 1 38 28 >> ",sep="",header=TRUE) >> >> res2<-do.call(rbind,lapply(split(dat2,list(dat2$Subject,dat2$Block)),function(x) >> data.frame(unique(x[,1:2]),t(colMeans(x[,-c(1:3)]))))) >> res2<-do.call(rbind,split(res2,res2$Subject)) >> res2 >> # Subject Block Feature1 Feature2 >> #1 1 1 55.0 29.0 >> #2 1 2 42.5 38.5 >> #3 1 3 64.0 14.0 >> #4 2 1 51.0 25.0 >> #5 2 2 56.5 45.0 >> #6 2 3 38.0 28.0 >> >> >> >> A.K. >> >> >> >> ----- Original Message ----- >> From: Johannes Brand <brandjohannes at gmx.de> >> To: r-help at r-project.org >> Cc: >> Sent: Thursday, February 21, 2013 12:02 PM >> Subject: [R] remove rows in data frame by average >> >> Dear all, >> >> I have a data frame, which looks like this: >> >> Subject | Block | Trial | Feature1 | Feature2 .... >> 1 | 1 | 1 | ... | ... >> 1 | 1 | 2 | ... | ... >> 1 | 2 | 1 | ... | ... >> 1 | 2 | 2 | ... | ... >> 1 | 3 | 1 | ... | ... >> ...| ...| ...| ... | ... >> >> Can I remove the "Trial" column by averaging all the rows and without using >> a "for loop"? >> >> At the end my data frame should look like this: >> >> Subject | Block | Feature1 | Feature2 .... >> 1 | 1 | ... | ... >> 1 | 2 | ... | ... >> 1 | 3 | ... | ... >> ...| ...| ... | ... >> >> Thank you a lot for your help. >> >> Best, >> Johannes >> David Winsemius Alameda, CA, USA