[R] Loop

[David Winsemius]

On Nov 4, 2010, at 9:21 AM, Matevž Pavlič wrote:

> Hi David,
>
> I am still having troubles with that loop ...
>
> This code gives me (kinda) the name of the column/field in a data  
> frame. Filed names are form W1-W10. But there is a space between W  
> and a number --> "W 10", and column (field) names do not contain  
> numbers.
>
>> for(i in 1:10)
>> {
>> vari <- paste("W",i)

Should be:

vari <- paste("w", i, sep="")


>> }
>> vari
>
> [1] "W 10"


>
> Now as i understand than i would call different columns to R with
>
>> w<-lit[[vari]]
>
> Or am i wrong again?

Maybe. Since you overwrote the first nine values there is only one  
element in vari outside the loop. I would do the assignment inside the  
loop and I suggested that the results be store in a list that is  
indexed either by "vari" or by "i" (but without the quotes if you are  
typing lit[[vari]]

-- 
David.
>
> Then I would probably need another loop to create the names of the  
> variables on R, i.e. w1 to w10. Is that a general idea for the  
> procedure?
>
>
> Thank for the help, m
>
> -----Original Message-----
> From: David Winsemius [mailto:dwinsemius at comcast.net]
> Sent: Wednesday, November 03, 2010 10:41 PM
> To: Matevž Pavlič
> Cc: r-help at r-project.org
> Subject: Re: [R] Loop
>
>
> On Nov 3, 2010, at 5:03 PM, Matevž Pavlič wrote:
>
>> Hi,
>>
>> Thanks for the help and the manuals. Will come very handy i am sure.
>>
>> But regarding the code i don't hink this is what i  
>> want....basically i
>> would like to repeat bellow code :
>>
>> w1<-table(lit$W1)
>> w1<-as.data.frame(w1)
>
> It appears you are not reading for meaning. Burns has advised you  
> how to construct column names and use them in your initial steps.  
> The `$` function is quite limited in comparison to `[[` , so he was  
> showing you a method that would be more effective.  BTW the  
> as.data.frame step is unnecessary, since the first thing write.table  
> does is coerce an object to a data.frame. The "write.table" name is  
> misleading. It should be "write.data.frame". You cannot really write  
> tables with write.table.
>
> You would also use:
>
>  file=paste(vari, "csv", sep=".") as the file argument to write.table
>
>> write.table(w1,file="w1.csv",sep=";",row.names=T, dec=".")
>
> What are these next actions supposed to do after the file is written?
> Are you trying to store a group of related "w" objects that will  
> later be indexed in sequence? If so, then a list would make more  
> sense.
>
> --
> David.
>
>> w1<- w1[order(w1$Freq, decreasing=TRUE),] w1<-head(w1, 20)
>>
>> 20 times, where W1-20 (capital letters) are the fields in a  
>> data.frame
>> called "lit" and w1-20 are the data.frames being created.
>>
>> Hope that explains it better,
>
>> m
>>
>> -----Original Message-----
>> From: Patrick Burns [mailto:pburns at pburns.seanet.com]
>> Subject: Re: [R] Loop
>>
>> If I understand properly, you'll want
>> something like:
>>
>> lit[["w2"]]
>>
>> instead of
>>
>> lit$w2
>>
>> more accurately:
>>
>> for(i in 1:20) {
>> vari <- paste("w", i)
>> lit[[vari]]
>>
>> ...
>> }
>>
>> The two documents mentioned in my
>> signature may help you.
>>
>> On 03/11/2010 20:23, Matevž Pavlič wrote:
>>> Hi all,
>>>
>>> I managed to do what i want (with the great help of thi mailing
>>> list)  manually . Now i would like to automate it. I would probably
>>> need a for loop for to help me with this...but of course  I have no
>>> idea how to do that in R.  Bellow is the code that i would like to  
>>> be
>>> replicated for a number of times (let say 20). I would like to
>>> achieve  that w1 would change to w2, w3, w4 ... up to w20 and by  
>>> that
>>> create 20 data.frames that I would than bind together with cbind.
>>>
>>> (i did it like shown bellow -manually)
>>>
>>> w1<-table(lit$W1)
>>> w1<-as.data.frame(w1)
>>> write.table(w1,file="w1.csv",sep=";",row.names=T, dec=".")
>>> w1<- w1[order(w1$Freq, decreasing=TRUE),] w1<-head(w1, 20)
>>>
>>> w2<-table(lit$W2)
>>>
>>> w2<-as.data.frame(w2)
>>>
>>> write.table(w2,file="w2.csv",sep=";",row.names=T, dec=".")
>>>
>>> w2<- w2[order(w2$Freq, decreasing=TRUE),]
>>>
>>> w2<-head(w2, 20)
>>> .
>>> .
>>> .
>>>
>>> Thanks for the help,m
>
>>
>
> David Winsemius, MD
> West Hartford, CT
>

David Winsemius, MD
West Hartford, CT