[R] Aggregate data frame across columns

[arun]

HI,

Without data, it is a bit hard to know how your data looks like.  


Anyway, try this:
set.seed(1)
dat2<-data.frame(matrix(sample(10:150,50,replace=TRUE),ncol=10))
names(dat2)<-c(paste0("20040",1:4),paste0("20050",1:3),paste0("20080",1:3))
library(reshape)
dat3<-melt(dat2)
dat3$variable<-gsub("(\\d{4}).*","\\1",dat3$variable)
 tapply(dat3$value,dat3$variable,FUN=sum)
#2004 2005 2008 
#1756 1094 1377 
#or
with(dat3,aggregate(value,by=list(variable),sum))
#  Group.1    x
#1    2004 1756
#2    2005 1094
#3    2008 1377
A.K.




----- Original Message -----
From: Keith Weintraub <kw1958 at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, November 7, 2012 12:32 PM
Subject: [R] Aggregate data frame across columns

Folks,
  I have a data frame with columns 200401, 200402, ..., 201207, 201208.

These represent years/months. What would be the best way to sum these columns by year? What about by quarter?

Thanks for your time,
KW

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