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How to re-combine values based on an index?

6 messages · Brian Feeny, William Dunlap, arun +1 more

Brian Feeny
# 
I am able to split my df into two like so:

dataset <- trainset
index <- 1:nrow(dataset)
testindex <- sample(index, trunc(length(index)*30/100))
trainset <- dataset[-testindex,]
testset <- dataset[testindex,-1]

So I have the index information, how could I re-combine the data using that back into a single df?

I tried what I thought might work, but failed with:

newdataset[testindex] = testset[testindex]
  object 'dataset' not found
newdataset[-testindex] = trainset[-testindex]
  object 'dataset' not found

Brian
William Dunlap
# 
Is that really what R printed?  I get
  > newdataset[testindex] = testset[testindex]
  Error in newdataset[testindex] = testset[testindex] : 
    object 'newdataset' not found
but perhaps you have a different problem.  Copy and paste
(and read) the error message you got.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
Brian Feeny
# 
Thank you for your response,  here is a better example of what I am trying to do:

data(iris)
index_setosa <- which(iris$Species == "setosa")
iris_setosa <- data.frame()
iris_setosa[index_setosa,] <-iris[index_setosa,]
iris_others <- data.frame()
iris_others[-index_setosa,] <- iris[-index_setosa,]

So the idea would be that iris_setosa is a dataframe of size 150, with 50 observations of setosa,
using their original same indices, and 100 observations of NA.  Likewise iris_others would be
100 observations of species besides setosa, using their original indices, and there would be 50 NA's.

The above doesn't work.  When I execute it, I am left with iris_setosa having 0 columns, I wish it to have all 
the original columns of iris.

That said, once I get past the above (being able to split them out and keep original indices), I wish to be able to combine
iris_setosa and iris_others so that iris_combined is a data frame with no NA's and all the original data.

Does this make sense?  So I am basically taking a dataframe, splitting it based on some criteria, and working on the two
split dataframes separately, and then I wish to recombine.

Brian


So at this point, I have iris_setosa a dataframe of size
On Dec 1, 2012, at 11:34 PM, William Dunlap wrote:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      arun
    

    

      
      #
    

  


  

      
Hi,
?merge(), ?rbind(), or ?join() from library(plyr)
set.seed(5)
trainset<-data.frame(ID=1:10,col2=runif(10,0,1))
?dataset <- trainset
?trainset<-dataset[-testindex,]
testset<-dataset[testindex,]
merge(testset,trainset,by=c("ID","col2"),all=TRUE)
#?? ID????? col2
#1?? 1 0.2002145
#2?? 2 0.6852186
#3?? 3 0.9168758
#4?? 4 0.2843995
#5?? 5 0.1046501
#6?? 6 0.7010575
#7?? 7 0.5279600
#8?? 8 0.8079352
#9?? 9 0.9565001
#10 10 0.1104530

You can also do this as:
?newdataset<-data.frame(ID=rep(NA,nrow(dataset)),col2=rep(NA,nrow(dataset)))
?newdataset[testindex,]<-testset
newdataset[-testindex,]<-trainset
?head(newdataset)
#? ID????? col2
#1? 1 0.2002145
#2? 2 0.6852186
#3? 3 0.9168758
#4? 4 0.2843995
#5? 5 0.1046501
#6? 6 0.7010575

A.K.




----- Original Message -----
From: Brian Feeny <bfeeny at mac.com>
To: r-help at r-project.org
Cc: 
Sent: Saturday, December 1, 2012 11:04 PM
Subject: [R] How to re-combine values based on an index?

I am able to split my df into two like so:

dataset <- trainset
index <- 1:nrow(dataset)
testindex <- sample(index, trunc(length(index)*30/100))
trainset <- dataset[-testindex,]
testset <- dataset[testindex,-1]

So I have the index information, how could I re-combine the data using that back into a single df?

I tried what I thought might work, but failed with:

newdataset[testindex] = testset[testindex]
? object 'dataset' not found
newdataset[-testindex] = trainset[-testindex]
? object 'dataset' not found

Brian

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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

  
  


  


      

    

    

      
      

        


  

        

      Berend Hasselman
    

    

      
      #
    

  


  

      
On 02-12-2012, at 06:06, Brian Feeny wrote:

        

            

      
      
      
    

        
Change you example to make it actually do something

data(iris)
index_setosa <- which(iris$Species == "setosa")
iris_setosa <-iris[index_setosa,]
head(iris_setosa)

# iris_others <- data.frame()
# iris_others[-index_setosa,] <- iris[-index_setosa,]
iris_others <- iris[-index_setosa,]
head(iris_others)
tail(iris_others)

The head() and tail() calls are for checking.
Combine the two like this

z <- rbind(iris_setosa,iris_others)
head(z)
tail(z)

Berend