[datatable-help] Fail to add new columns within a function

[Matt Dowle]

Why are you doing this iteratively?  Can't you load all the files into a 
list,  rbindlist and then reshape?

On 18/12/13 09:04, Huashan Chen wrote:
> OK, here is the complete code with some mock functions from my example.
>
> # data: data.table object
> # fn: a filename to read data from
> merge_data<-function(fn, data){
>    fs<-getSavedata(fn) # read as data.frame
>    if (is.null(fs)) stop('Empty data file')
>    
>    # return a character vector of variable names which are to merged, some
> variables in fs will not be merged to DT
>    newvars<-selectVars(names(fs))
>    stopifnot(length(newvars) > 0)
>      
>      # determine which rows to use
>      caseid<-someCustomFunc(fs)
>    
>    add_var<-function(varname){
>        data[caseid, `:=`(eval(substitute(varname)), fs[,
> toupper(eval(substitute(varname)))]), with=F]
>      }
>      invisible(sapply(newvars, add_var))
> }
>
> # calling function
> merge_data('some file', DT)
> DT # display the updated results
>
>
> In this case, I think a warning from merge_data() when the quota is reached
> would be appreciated. Of couse, I could have added a check within the
> function to avoid unintended action.
>
>      if (truelength(data) <= ncol(data) + 64L) stop('increase colunmn quota
> using alloc.col() before calling this function.')
>
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Fail-to-add-new-columns-within-a-function-tp4682173p4682393.html
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