Question

I’m trying to subset, in a big file, all the words that DO NOT end with "_at".

For example: the file “myfile” is a data.frame composed as follow (specifically I have a file with 50 columns and 1000 rows):

myfile <- read.table( text = '"G1"            "G2"  
    SEP11          ABCC1   
    205772_s_at    FMO2   
    214223_at      ADAM19     
    ANK2           215742_at 
    COPS4          BIK 
    214808_at      DCP1A
    ACE            ALG3
    BAD            215369_at
    EMP3           215385_at
    CARD8          217579_x_at
', header = TRUE, stringsAsFactors = FALSE)

I would like the following output:

  "G1"           "G2"  
 SEP11          ABCC1  
 ANK2           FMO2  
 COPS4          ADAM19     
 ACE            BIK   
 BAD            DCP1A
 EMP3           ALG3 
 CARD8

I used the following string but it doesn’t work probably because I’m doing something wrong:

sub <- myfile[-grep("\\_at", names(myfile)), ]

Can anyone help me?

Answer 1

The following code will give you a list. Each element of the list being a subset of one of your column filtered by the regular expression _at$. See ?grep .

lapply( myfile, 
   function(column) grep( "_at$", column, invert = TRUE, value = TRUE )
)