Creating new table from a big .csv table

Question

I have big .csv file. I would like to filter that file into a new table.

For example, I have .csv file as below:

   f1 f2  f3 f4  f5  f6 f7 f9  f10  f1         


        

Answer 1

 sapply(1:nrow(dat), function(x) if (dat[x, "f1"]==1) { 
           write.csv( dat[ (dat[["f1"]]==1 )& (1:nrow(dat) >= x) , ])
            } else {NULL} )
"","f1","f2","f3","f4","f5","f6","f7","f9","f10","f11"
"t1",1,0,1,0,1,0,0,0,0,1
"t2",1,0,0,0,0,1,1,1,1,1
"t4",1,0,0,0,1,0,0,0,0,0
"","f1","f2","f3","f4","f5","f6","f7","f9","f10","f11"
"t2",1,0,0,0,0,1,1,1,1,1
"t4",1,0,0,0,1,0,0,0,0,0
"","f1","f2","f3","f4","f5","f6","f7","f9","f10","f11"
"t4",1,0,0,0,1,0,0,0,0,0
[[1]]
NULL

Will need to construct file names:

invisible(
  sapply(1:nrow(dat), function(x) if (dat[x, "f1"]==1) { 
           write.csv( dat[ (dat[["f1"]]==1 )& (1:nrow(dat) >= x) , ] ,
                    file = paste0("fil_", x, ".csv") )
                                } else {NULL} )
         )   

If this is destined for Excel, as I fear it might be, note that the rownames are included but no column header will be created to designate the rownames.