r - Subset variables in data frame based on column type -


i need subset data frame based on column type - example data frame 100 columns need keep column type factor or integer. i've written short function this, there simpler solution or built-in function or package on cran?

my current solution variable names requested types:

varlist <- function(df=null, vartypes=null) {   type_function <- c("is.factor","is.integer","is.numeric","is.character","is.double","is.logical")   names(type_function) <- c("factor","integer","numeric","character","double","logical")   names(df)[as.logical(sapply(lapply(names(df), function(y) sapply(type_function[names(type_function) %in% vartypes], function(x) do.call(x,list(df[[y]])))),sum))]   }

the function varlist works follows:

  1. for every requested type , every column in data frame call "is.type" function
  2. sum tests every variable (boolean casted integer automatically)
  3. cast result logical vector
  4. subset names in data frame

and data test it:

df <- read.table(file="http://archive.ics.uci.edu/ml/machine-learning-databases/statlog/german/german.data", sep=" ", header=false, stringsasfactors=true) names(df) <- c('ca_status','duration','credit_history','purpose','credit_amount','savings', 'present_employment_since','installment_rate_income','status_sex','other_debtors','present_residence_since','property','age','other_installment','housing','existing_credits', 'job','liable_maintenance_people','telephone','foreign_worker','gb') df$gb <- ifelse(df$gb == 2, false, true) df$property <- as.character(df$property) varlist(df, c("integer","logical"))

i'm asking because code looks cryptic , hard understand (even me , i've finished function 10 minutes ago).

subset_colclasses <- function(df, colclasses="numeric") {   df[,sapply(df, function(vec, test) class(vec) %in% test, test=colclasses)] }  str(subset_colclasses(df, c("factor", "integer")))

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