R help - Mar 2011 - Exporting columns into multiple files - loop query

Hi,

I'm using a loop to extract 2 columns from an array into multiple files. 
I can use the following to export 3 files, containing column 'ID' with
one of
the three event columns.
>
ID<-c("A","B","C","D","E","F")
> event1<-c(0,1,0,0,1,0)
> event2<-c(1,1,0,1,0,0)
> event3<-c(1,0,1,0,1,0)
> data<-cbind(ID,event1,event2,event3)
> data
     ID  event1 event2 event3
[1,] "A" "0"    "1"    "1"   
[2,] "B" "1"    "1"    "0"   
[3,] "C" "0"    "0"    "1"   
[4,] "D" "0"    "1"    "0"   
[5,] "E" "1"    "0"    "1"   
[6,] "F" "0"    "0"    "0"   

The data represent individuals that are either seen (1) or not seen (0) on
several occasions.
> 
> n<-ncol(data)
> 
> for(i in 2:n) {
+ df<-data.frame(data[,i],ID) 
+ myfile<-gsub("( )", "",paste(i,".txt")) #
name file by year
+ write.table(df, file=myfile,
sep="\t",row.names=F,col.names=F,quote=FALSE,append=FALSE) 
+ }  

My question: How can I add a function to this loop, to delete rows in the
data frame in which the event is equal to zero? 

An desired file output would be:
     ID  event2
[1,] "A" "1"      
[2,] "B" "1"      
[3,] "D" "1"   

I can handle this taking each file separately using subscripts, but my
attempts to amend the loop, and be able to run this code on a bunch of large
mutliple event files, have failed.

With grateful thanks in advance,

Matt

--
Matt Wood
Department of Natural and Social Sciences
University of Gloucestershire
Francis Close Hall
Cheltenham 
GL50 4AZ



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On Mar 25, 2011, at 10:45 PM, WOOD, Matthew wrote:
> Hi,
>
> I'm using a loop to extract 2 columns from an array into multiple  
> files.
> I can use the following to export 3 files, containing column 'ID'  
> with one of
> the three event columns.
>
>>
ID<-c("A","B","C","D","E","F")
>> event1<-c(0,1,0,0,1,0)
>> event2<-c(1,1,0,1,0,0)
>> event3<-c(1,0,1,0,1,0)
>> data<-cbind(ID,event1,event2,event3)
>> data
>     ID  event1 event2 event3
> [1,] "A" "0"    "1"    "1"
> [2,] "B" "1"    "1"    "0"
> [3,] "C" "0"    "0"    "1"
> [4,] "D" "0"    "1"    "0"
> [5,] "E" "1"    "0"    "1"
> [6,] "F" "0"    "0"    "0"
>
> The data represent individuals that are either seen (1) or not seen  
> (0) on
> several occasions.
>>
>> n<-ncol(data)
>>
>> for(i in 2:n) {
> + df<-data.frame(data[,i],ID)
> + myfile<-gsub("( )", "",paste(i,".txt"))
# name file by year
> + write.table(df, file=myfile,
> sep="\t",row.names=F,col.names=F,quote=FALSE,append=FALSE)
> + }
>
> My question: How can I add a function to this loop, to delete rows  
> in the
> data frame in which the event is equal to zero?
>
Since the expression data[,i] is returning a vector,you could just use  
its values to filter both the "data" and the "ID" vectors:

for(i in 2:n) {
  df<-data.frame( data[,i][data[,i]!=0], ID[data[,i]!=0] )
  myfile<-gsub("( )", "",paste(i,".txt")) #
name file by year
  write.table(df, file=myfile,
sep="\t",row.names=F,col.names=F,quote=FALSE,append=FALSE)
  }


Or you could filter just the data.frame with "[":

for(i in 2:n) {
  df<-data.frame(data[,i],ID)[ data[,i]!=0, ]
  myfile<-gsub("( )", "",paste(i,".txt")) #
name file by year
  write.table(df, file=myfile,
sep="\t",row.names=F,col.names=F,quote=FALSE,append=FALSE)
  }

There are probably more elegant ways but you do now have method that  
"work".

-- 
David.
> An desired file output would be:
>     ID  event2
> [1,] "A" "1"
> [2,] "B" "1"
> [3,] "D" "1"
>
> I can handle this taking each file separately using subscripts, but my
> attempts to amend the loop, and be able to run this code on a bunch  
> of large
> mutliple event files, have failed.
>
> With grateful thanks in advance,
>
> Matt
>
> --
> Matt Wood
> Department of Natural and Social Sciences
> University of Gloucestershire
> Francis Close Hall
> Cheltenham
> GL50 4AZ
>
>
>
> 'In the top three in the People and Planet green league table;  
> committed to sustainability'
>
> This email is confidential to the intended recipient. If you have  
> received it in error please notify the sender and delete it from  
> your computer.
>
> The University of Gloucestershire is a company limited by guarantee  
> registered in England and Wales. Registered number: 06023243  
> Registered office: The Park, Cheltenham, GL50 2RH
>
> Please consider the environment before printing this email.
>
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West Hartford, CT