Function for converting dataframe column type

Question

R often understands data frame columns in a \"wrong\" format or you just have to change the column class from factor to character in order to modify it. I have been changing

Answer 1

df <- data.frame(x = 1:10,
                 y = rep(1:2, 5),
                 k = rnorm(10, 5,2),
                 z = rep(c(2010, 2012, 2011, 2010, 1999), 2),
                 j = c(rep(c("a", "b", "c"), 3), "d"))

convert.magic <- function(obj, type){
  FUN1 <- switch(type,
                 character = as.character,
                 numeric = as.numeric,
                 factor = as.factor)
  out <- lapply(obj, FUN1)
  as.data.frame(out)
}

str(df)
str(convert.magic(df, "character"))
str(convert.magic(df, "factor"))
df[, c("x", "y")] <- convert.magic(df[, c("x", "y")], "factor")