Create column spec for a data frame not already read in by readr

create_spec.R

create_spec <- function(x,condense = TRUE){
  v_inherits <- Vectorize(FUN = inherits,vectorize.args = "what")
  col_map <- c(logical = "l",
               integer = "i",
               numeric = "d",
               factor = "f",
               character = "c",
               Date = "D",
               POSIXct = "T")
  x_spec <- rep("?",times = ncol(x))
  
  for (i in seq_along(x)){
    cl <- col_map[which(v_inherits(x[[i]],names(col_map)))]
    if (length(cl) == 1){
      x_spec[i] <- cl
    }
  }

  x_spec <- do.call(readr::cols,as.list(setNames(x_spec,colnames(x))))
  
  if (condense){
    x_spec <- readr::cols_condense(x_spec)
  }
  x_spec
}

dat <- data.frame(x1 = 1:5,
                  x2 = letters[1:5],
                  x3 = sample(c(T,F),size = 5,replace = TRUE),
                  x4 = LETTERS[1:5],
                  x5 = Sys.Date() + 1:5,
                  x6 = Sys.time() + 1:5,
                  x7 = runif(5),
                  x8 = I(list(a = 1:2,b = 3:4,c = 1:2,d = 1,e = "a")))
dat$x4 <- as.character(dat$x4)

create_spec(dat)
create_spec(dat,condense = FALSE)