I got this in `/usr/local/share/doc/ranger/examples/vim_file_chooser.vim`.

    " Compatible with ranger 1.4.2 through 1.6.*
    "
    " Add ranger as a file chooser in vim
    "
    " If you add this function and the key binding to the .vimrc, ranger can be
    " started using the keybinding ",r".  Once you select a file by pressing
    " enter, ranger will quit again and vim will open the selected file.

    fun! RangerChooser()
        exec "silent !ranger --choosefile=/tmp/chosenfile " . expand("%:p:h")
        if filereadable('/tmp/chosenfile')
            exec 'edit ' . system('cat /tmp/chosenfile')
            call system('rm /tmp/chosenfile')
        endif
        redraw!
    endfun
    map ,r :call RangerChooser()<CR>