[R] Help avoiding setting column type two times

[Gerrit Eichner]

See below.

Am 30.11.2017 um 15:27 schrieb Martin Møller Skarbiniks Pedersen:
> Hi,
>    I think and hope this a good place to ask for code review for a R
> beginners?
> 
>    I have made a R script which generates a dataset based on 2009 danish
> referendum and it does work.
> 
>    But I think the code could be better and I would any comments how the
> code can be improved.
>    At least I would like to know how I avoid converting several of the
> columns to factors in the end of the code?
> 
> Description of the code:
> 
>    It reads a lot of xml-files from ../raw/ and saves a data.frame with
> information
> from these xml-files.
> 
>    In the ../raw/ directiory I have placed the xml-files which I got from
> "Statistics Denmark"
>    I have also put these xml-files on my website and they can be download
> freely from http://20dage.dk/R/referendum-2009/raw.tar.gz
> 
>    The code is below but I have also put the code at this place:
> http://20dage.dk/R/referendum-2009/convert_from_xml.R
> 
> Best Regards
> Martin M. S. Pedersen
> 
> -------
> library(xml2)
> 
> convert_one_file <- function(url) {
>      x <- read_xml(url)
> 
>      Sted <- xml_find_first(x, ".//Sted")
>      StedType <- xml_attr(Sted, "Type")
>      StedTekst <- xml_text(Sted)
> 
>      Parti <- xml_find_all(x, ".//Parti")
>      PartiId <- xml_attr(Parti, "Id")
>      PartiBogstav <- xml_attr(Parti, "Bogstav")
>      PartiNavn <- xml_attr(Parti, "Navn")
> 
> 
>      StemmerAntal <- xml_attr(Parti, "StemmerAntal")
>      Stemmeberettigede <- xml_integer(xml_find_first(x,
> ".//Stemmeberettigede"))
>      DeltagelsePct <- xml_double(xml_find_first(x, ".//DeltagelsePct"))
>      IAltGyldigeStemmer <- xml_integer(xml_find_first(x,
> ".//IAltGyldigeStemmer"))
>      BlankeStemmer <- xml_integer(xml_find_first(x, ".//BlankeStemmer"))
>      AndreUgyldigeStemmer <- xml_integer(xml_find_first(x,
> ".//AndreUgyldigeStemmer"))
> 
>      data.frame(cbind(StedType, StedTekst, PartiId, PartiBogstav, PartiNavn,
>                   StemmerAntal, Stemmeberettigede, DeltagelsePct,
> IAltGyldigeStemmer,
>         BlankeStemmer, AndreUgyldigeStemmer), stringsAsFactors = FALSE)
> }
> 
> raw_path <- "../raw"
> filenames <- dir(path = raw_path, pattern = "fintal_.*", full.names = T)
> 
> result <- data.frame(StedType = factor(),
>                       StedTekst = character(),
>                       PartiId   = factor(),
>                       PartiBogstav = factor(),
>                       PartiNavn    = factor(),
>                       StemmerAntal = integer(),
>                       Stemmeberettigede = integer(),
>                       DeltagelsePct = numeric(),
>                       IAltGyldigeStemmer = integer(),
>                       BlankeStemmer = integer(),
>                       AndreUgyldigeStemmer = integer(),
>                       stringsAsFactors = FALSE)
> 
> for (i in 1:length(filenames)) {
>      #cat(paste0(filenames[i],"\n"))
>      returnCode <-  tryCatch({
>         result <- rbind(result, convert_one_file(filenames[i]))
>      }, error = function(e) {
>         cat(paste0(filenames[i]," failed:\n",e,"\n"))
>      })
> }
> 
> result$StedType <- as.factor(result$StedType)
> result$PartiId <- as.factor(result$PartiId)
> result$PartiBogstav <- as.factor(result$PartiBogstav)
> result$PartiNavn <- as.factor(result$PartiNavn)
> result$StemmerAntal <- as.integer(result$StemmerAntal)
> result$Stemmeberettigede <- as.integer(result$Stemmeberettigede)
> result$DeltagelsePct <- as.numeric(result$DeltagelsePct)
> result$IAltGyldigeStemmer <- as.integer(result$IAltGyldigeStemmer)
> result$BlankeStemmer <- as.integer(result$BlankeStemmer)
> result$AndreUgyldigeStemmer <- as.integer(result$AndreUgyldigeStemmer)
> str(result)
> save(result, file = "folkeafstemning2009.Rdata")

Maybe two loops simplify this a little bit for you (not tested):

for(v in c("StedType", <etc.>))
  result[[v]] <- factor(result[[v]])

for(v in c("StemmerAntal", <etc.>))
  result[[v]] <- as.integer(result[[v]])

  Hth  --  Gerrit

---------------------------------------------------------------------
Dr. Gerrit Eichner                   Mathematical Institute, Room 212
gerrit.eichner at math.uni-giessen.de   Justus-Liebig-University Giessen
Tel: +49-(0)641-99-32104          Arndtstr. 2, 35392 Giessen, Germany
Fax: +49-(0)641-99-32109            http://www.uni-giessen.de/eichner
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