[R] lapply getting names of the list

[David Winsemius]

On Dec 9, 2010, at 12:44 PM, Sashi Challa wrote:

> Hello All,
>
> I have a toy dataframe like this. It has 8 columns separated by tab.
>
> Name    SampleID        Al1     Al2     X       Y       R       Th
> rs191191        A1      A       B       0.999   0.09    0.78    0.090
> abc928291       A1      B       J       0.3838  0.3839  0.028   0.888
> abcnab  A1      H       K       0.3939  0.939   0.3939  0.77
> rx82922 B1      J       K       0.3838  0.393   0.393   0.00
> rcn3939 B1      M       O       0.000   0.000   0.000   0.77
> tcn39399        B1      P       I       0.393   0.393   0.393   0.56
>
> Note that the SampleID is repeating. So I want to be able to split  
> the dataset based on the SampleID and write the splitted dataset of  
> every SampleID into a new file.
> I tried split followed by lapply to do this.
>
> infile <- read.csv("test.txt", sep="\t", as.is = TRUE, header = TRUE)
> infile.split  <- split(infile, infile$SampleID)
> names(infile.split[1])  ## outputs “A1”
> ## now A1, B1 are two lists in infile.split as I understand it.  
> Correct me if I am wrong.
>
> lapply(infile.split,function(x){
>              filename <- names(x) #### here I expect to see A1 or  
> B1, I didn’t, I tried (names(x)[1]) and that gave me “Name” and not  
> A1 or B1.
>              final_filename <- paste(filename,”toy_set.txt”,sep=”_”)
>              write.table(x, file = paste(path,  
> final_filename,sep=”/”, row.names=FALSE, quote=FALSE,sep=”\t”)
>  } )
>
> In lapply I wanted to give a unique filename to all the split Sample  
> Ids, i.e. name them here as <dragged to the c() construct>.
> How do I get those names, i.e. A1, B1 to a create a filename like  
> above.

names(file.split) <- c("A1_toy_set.txt", "B1_toy_set_txt")

> When I write each of the element in the list obtained after split  
> into a file,

How are you proposing do do this "writing"?

> the column names would have names like A1.Name, A1.SampleID, A1.Al1,  
> …..

Are you sure? Why would you think that?

-- 
David.

> Can I get rid of “A1” in the column names within the lapply (other  
> than reading in the file again and changing the names) ?
>
> Thanks for your time,
>
> Regards
> Sashi
>
>
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>
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David Winsemius, MD
West Hartford, CT