[R] Excluding fixed number of rows from calculation while summarizing using ddply() function.

[arun]

dat1<-read.table(text="
Unique,StepNo,Data1,Data2
A,1,4,5   
A,1,5,6
A,1,7,8   
A,2,9,10  
A,2,45,25
A,2,10,11 
B,2,34,12 
B,2,5,6
B,2,7,8
B,2,6,7  
B,3,1,2  
B,3,3,4
B,3,4,5  
",sep=",",header=TRUE,stringsAsFactors=FALSE)


dat2<-ddply(dat1,.(Unique,StepNo),function(x) x[c(1,nrow(x)),])

  dat1$newcoldat1<-TRUE
 dat2$newcoldat2<-TRUE
 dat3<-merge(dat1,dat2,all=TRUE)
dat4<-dat3[is.na(dat3$newcoldat2),1:4]

dat4
#   Unique StepNo Data1 Data2
#2       A      1     5     6
#6       A      2    45    25
#7       B      2     5     6
#9       B      2     7     8
#12      B      3     3     4

 ddply(dat4,.(Unique,StepNo),numcolwise(mean))
#  Unique StepNo Data1 Data2
#1      A      1     5     6
#2      A      2    45    25
#3      B      2     6     7
#4      B      3     3     4

A.K.

----- Original Message -----
From: siddu479 <onlyfordigitalstuff at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Sunday, November 4, 2012 9:40 AM
Subject: [R] Excluding fixed number of rows from calculation while summarizing using ddply() function.

Hello All,

   I have a .csv file( contents shown) below, where I need to calculate
mean(for example) for only the rows highlighted in bold. (i.e. in this
example case I need to exclude the first row and last row(N=1) for each
"*StepNo*" column)

Unique,StepNo,Data1,Data2    #In actual file I have 100 columns and nearly
millions of rows.
A,1,4,5           #Exclude this 1st row for this "StepNo" and "Unique"
combination.
*A,1,5,6 *
A,1,7,8           #Exclude this last row for this "StepNo" and "Unique"
combination.
A,2,9,10         #Exclude this row because this 1st row for this "StepNo"
and "Unique" combination. 
*A,2,45,25*
A,2,10,11      #Exclude this last row for this "StepNo" and "Unique"
combination.
B,2,34,12      #Exclude this 1st row for this "StepNo" and "Unique"
combination. 
*B,2,5,6
B,2,7,8*
B,2,6,7           #Exclude this last row for this "StepNo" and "Unique"
combination.
B,3,1,2           #Exclude this 1st row for this "StepNo" and "Unique"
combination.
*B,3,3,4*
B,3,4,5          #Exclude this last row for this "StepNo" and "Unique"
combination.

My existing code to calculate mean* for all rows* is 
dat <- read.csv("aboveinput.csv", header=T) #Loading Input file
library("plyr")  
*result <- ddply(dat, .(Unique,StepNo), numcolwise(mean))*   # Calculating
mean for each Unique and StepNo combination and summarizing the results.

*I need to modify the above script to exclude some "N number of rows at the
start as well as at the end of each StepNo"*
Something like result <- ddply(dat, .(Unique,StepNo),numcolwise(mean(head n
rows excluded, tail n rows excluded in each StepNo)))  #Just a skeleton
script.

Please revert to me if my question is not clear.







-----
Sidda
Business Analyst Lead
Applied Materials Inc.

--
View this message in context: http://r.789695.n4.nabble.com/Excluding-fixed-number-of-rows-from-calculation-while-summarizing-using-ddply-function-tp4648406.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.