[R] combine two columns into one

[arun]

dat1<- read.table(text="
Date       Time    Var             
11/1/2012   1      3    
11/1/2012    1      1      
 11/1/2012   1      1     
11/1/2012    2      3      
11/1/2012    2      1     
 11/1/2012   2      1    
11/2/2012   1      1      
 11/2/2012   1     3     
11/2/2012   1      1      
 11/2/2012   2     3
",sep="",header=TRUE,stringsAsFactors=FALSE)
 dat1$Date<-as.Date(dat1$Date,format="%m/%d/%Y")

If you need to combine Date and Time columns into one:
library(plyr)
res<-mutate(ddply(dat1,.(Date,Time),summarize,Var=sum(Var)),DT=paste(Date,Time,sep="_"))[,c(4,3)]
 res
#            DT Var
#1 2012-11-01_1   5
#2 2012-11-01_2   5
#3 2012-11-02_1   5
#4 2012-11-02_2   3
A.K.






________________________________
From: Ye Lin <yelin at lbl.gov>
To: arun <smartpink111 at yahoo.com> 
Cc: R help <r-help at r-project.org> 
Sent: Wednesday, May 29, 2013 2:40 PM
Subject: Re: [R] combine two columns into one



The actual  "date" col is in yyyy-mm-dd format, and when I apply this code to my actual data, it mess up the order



On Wed, May 29, 2013 at 11:37 AM, arun <smartpink111 at yahoo.com> wrote:


>
>Hi,
>May be I misunderstood your question:
>dat<- read.table(text="
>
>Date    Time  Var
>1            1        2
>1          1        4
>1          1        5
>1          2          8
>1          2          8
>1        2          9
>2        1            3
>2        1              4
>2        1            4
>",sep="",header=TRUE)
>
>dat$UniqueID <- paste(dat$Date,dat$Time, sep = '_')
> aggregate(dat$Var,list(dat$UniqueID),sum) #isn't this the correct order
>#  Group.1  x
>#1     1_1 11
>#2     1_2 25
>#3     2_1 11
>library(plyr)
>ddply(dat,.(UniqueID),summarize,Var=sum(Var))
>#  UniqueID Var
>#1      1_1  11
>#2      1_2  25
>#3      2_1  11
>A.K.
>
>
>
>
>----- Original Message -----
>From: Ye Lin <yelin at lbl.gov>
>To: R help <r-help at r-project.org>
>Cc:
>Sent: Wednesday, May 29, 2013 2:23 PM
>Subject: [R] combine two columns into one
>
>Hey all!
>
>I have a time series dataset like this:
>
>Date    Time   Var
>1            1        2
>1           1        4
>1           1         5
>1          2          8
>1          2          8
>1         2           9
>2        1            3
>2        1              4
>2        1            4
>
>I created a unique id for each row:
>dat$UniqueID <- paste(dat$Date,dat$Time, sep = '_')
>
>then
>
>aggregate(dat$Var, list(dat$UniqueID), sum)
>
>however the final output is not in ideal order I look for (I simply this
>example provided above).I would like to have order like this:
>
>1_1
>1_2
>2_1
>
>Thanks for your help!
>
>    [[alternative HTML version deleted]]
>
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