attributes_to_columns.R

# put each attribute into a column if possible
# rownames_to_column: (logical) add rownames if the attribute exists
# fix_name_conflicts: (logical) if an attribute name already exists as a column name, find a unique name for it
attributes_to_columns = function(dataframe, rownames_to_column = TRUE, fix_name_conflicts = TRUE) {
    for (name in names(attributes(dataframe))) {
      
      value = attr(dataframe, name)
      
      if (name %in% c("names", "class")) {
        #skip
      }
      else if (name == "row.names") {
        # TODO: check duplicate column name
        if (rownames_to_column)
          dataframe = dataframe %>% rownames_to_column()
      }
      else if (!is.vector(value)) {
        warning(
          name, ": Skipping attribute because it is of type ", class(value),
          "\nOnly vectors can be added as a column.")
      }
      else if (length(value) == 1 || length(value) == nrow(dataframe)) {
        # if not fixing name conflicts and there is one
        if (!fix_name_conflicts && name %in% names(dataframe)) {
          warning(
            name, ": Skipping attribute because a column by that name already exists",
            "\nSet `fix_name_conflicts` to TRUE to automatically rename conflicting attributes.")
        }
        # ensure unqiue name
        while(name %in% names(dataframe))
          name = paste0("_", name)
        # TODO: check if class() can be stored in a data.frame
        # add the column
        dataframe[name] = value
      }
      else {
        # how to handle vectors with neither 1 nor nrow values?
        warning(
          name, ": Skipping attribute because it is of length ", length(value),
          "\nAttribute must be of length 1 or the tibble length to be added as a column.")
      }
    }
    
    dataframe
}


# make a simple tibble with attributes
temp = tibble( x=1:10, y=LETTERS[1:10], z=sample(factor(letters[1:3]), 10, TRUE))
attr(temp, "single_value") = "hello"
attr(temp, "many_values") = rnorm(10)
attr(temp, "double") = 1:2
attr(temp, "cars") = rownames_to_column(mtcars)[1:5,]

# view
print(temp)
attributes(temp)

# dataframe with attributes as columns (will warn about incompatible attributes)
temp %>% attributes_to_columns()

# automatically fix duplicate names
temp %>% attributes_to_columns() %>% attributes_to_columns(rownames_to_column = FALSE)

# warn for duplicate names
temp %>% attributes_to_columns() %>% attributes_to_columns(rownames_to_column = FALSE, fix_name_conflicts = FALSE)