将 .db 文件导入 R

Question

I am trying to import a .db file using the code below, which is the same as the example with the package and it says can't find function. Anyone have any idea on how to import a .db file?

library(ProjectTemplate)
db.reader('c3.db','/Users/xxx/Documents/c3.db','Data')

> db.reader('c3.db','/Users/xxx/Desktop/','Data')
Error: could not find function "db.reader"

Answer 1

I dont'use/have installed this package, however it seems this function is not exported and then not available to the user. From the NAMESPACE file

# Generated by roxygen2 (4.0.0): do not edit by hand

export(cache)
export(cache.project)
export(create.project)
export(get.project)
export(load.project)
export(reload.project)
export(require.package)
export(run.project)
export(show.project)
export(stub.tests)
export(test.project)
export(translate.dcf)

After all, the example is

## Not run: db.reader('example.db', 'data/example.db', 'example')

The function is, however

db.reader <- function(data.file, filename, variable.name)
{
  require.package('RSQLite')

  sqlite.driver <- dbDriver("SQLite")
  connection <- dbConnect(sqlite.driver,
                          dbname = filename)

  tables <- dbListTables(connection)
  for (table in tables)
  {
    message(paste('  Loading table:', table))

    data.parcel <- dbReadTable(connection,
                               table,
                               row.names = NULL)

    assign(clean.variable.name(table),
           data.parcel,
           envir = .TargetEnv)
  }

  disconnect.success <- dbDisconnect(connection)
  if (! disconnect.success)
  {
    warning(paste('Unable to disconnect from database:', filename))
  }
}

You could try to use it directly (from workspace), but best approach (IMHO) is

• eventually to ask the maintainer (why can't it be ran, currently? Excluding an error in NAMESPACE generation, I think db.reader could be a placeholder at the moment) OR
• if you used this package only for db file import, you could program your own RSQLite-based function (eg using this as a template)