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remove rows in data frame by average

5 messages · Johannes Brand, arun, Anthony Damico +2 more

Original
arun
# 
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

??? [[alternative HTML version deleted]]

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William Dunlap
# 
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. 

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
David Winsemius
#
On Feb 21, 2013, at 2:15 PM, William Dunlap wrote:

            

      
      
      
    

        
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:

            

      
      
      
    

        
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