Nvim-Rがないともうダメな体になってしまった。
さらに、Neocompleteが良いと聞き、導入したい。がしかし
・Nvim-Rにはvim8が必要
・NeocompleteはLuaが必要
・公式レポジトリ等にあるビルド済みvim8はLuaが有効になっていない
ということで、Lua有効のvim8を手に入れるため、ソースからビルドする必要がある。

前提
・vim-plugがインストールされていること
・GitHubにsshで接続できること

Luaが有効になったVIM8のビルド・インストール(参考)

sudo apt-get remove --purge vim vim-runtime vim-gnome vim-tiny vim-gui-common
sudo apt-get install liblua5.1-dev luajit libluajit-5.1 python-dev ruby-dev libperl-dev libncurses5-dev libatk1.0-dev libx11-dev libxpm-dev libxt-dev
sudo rm -rf /usr/local/share/vim
sudo rm /usr/bin/vim
sudo mkdir /usr/include/lua5.1/include
sudo cp /usr/include/lua5.1/*.h /usr/include/lua5.1/include/
cd /opt/
sudo git clone https://github.com/vim/vim
cd /opt/vim
sudo git pull
sudo git fetch
cd /opt/vim/src
sudo ./configure --with-features=huge \
            --enable-rubyinterp \
            --enable-largefile \
            --disable-netbeans \
            --enable-pythoninterp \
            --with-python-config-dir=/usr/lib/python2.7/config \
            --enable-perlinterp \
            --enable-luainterp \
            --with-luajit \
            --enable-fail-if-missing \
            --with-lua-prefix=/usr/include/lua5.1 \
            --enable-cscope   
sudo make 
cd /opt/vim
sudo make install

プラグインのインストール

~/.vimrcに追記

call plug#begin('~/.vim/plugged')
  Plug 'https://github.com/jalveseq/Nvim-R'
  Plug 'https://github.com/Shougo/neocomplete.vim'
call plug#end()

vimで下記コマンドを実行

:PlugInstall

~/.vimrcにNvim-Rの設定を追記

let R_tmux_split = 1
### let R_vsplit = 1　#NvimRのバージョンが変わって下記が推奨されています
let R_rconsole_width = winwidth(0) / 2
autocmd VimResized * let R_rconsole_width = winwidth(0) / 2

~/.vimrcにneocompleteの設定を追記(公式)

"Note: This option must be set in .vimrc(_vimrc).  NOT IN .gvimrc(_gvimrc)!
" Disable AutoComplPop.
let g:acp_enableAtStartup = 0
" Use neocomplete.
let g:neocomplete#enable_at_startup = 1
" Use smartcase.
let g:neocomplete#enable_smart_case = 1
" Set minimum syntax keyword length.
let g:neocomplete#sources#syntax#min_keyword_length = 3

" Define dictionary.
let g:neocomplete#sources#dictionary#dictionaries = {
    \ 'default' : '',
    \ 'vimshell' : $HOME.'/.vimshell_hist',
    \ 'scheme' : $HOME.'/.gosh_completions'
        \ }

" Define keyword.
if !exists('g:neocomplete#keyword_patterns')
    let g:neocomplete#keyword_patterns = {}
endif
let g:neocomplete#keyword_patterns['default'] = '\h\w*'

" Plugin key-mappings.
inoremap <expr><C-g>     neocomplete#undo_completion()
inoremap <expr><C-l>     neocomplete#complete_common_string()

" Recommended key-mappings.
" <CR>: close popup and save indent.
inoremap <silent> <CR> <C-r>=<SID>my_cr_function()<CR>
function! s:my_cr_function()
  return (pumvisible() ? "\<C-y>" : "" ) . "\<CR>"
  " For no inserting <CR> key.
  "return pumvisible() ? "\<C-y>" : "\<CR>"
endfunction
" <TAB>: completion.
inoremap <expr><TAB>  pumvisible() ? "\<C-n>" : "\<TAB>"
" <C-h>, <BS>: close popup and delete backword char.
inoremap <expr><C-h> neocomplete#smart_close_popup()."\<C-h>"
inoremap <expr><BS> neocomplete#smart_close_popup()."\<C-h>"
" Close popup by <Space>.
"inoremap <expr><Space> pumvisible() ? "\<C-y>" : "\<Space>"

" AutoComplPop like behavior.
"let g:neocomplete#enable_auto_select = 1

" Shell like behavior(not recommended).
"set completeopt+=longest
"let g:neocomplete#enable_auto_select = 1
"let g:neocomplete#disable_auto_complete = 1
"inoremap <expr><TAB>  pumvisible() ? "\<Down>" : "\<C-x>\<C-u>"

" Enable omni completion.
autocmd FileType css setlocal omnifunc=csscomplete#CompleteCSS
autocmd FileType html,markdown setlocal omnifunc=htmlcomplete#CompleteTags
autocmd FileType javascript setlocal omnifunc=javascriptcomplete#CompleteJS
autocmd FileType python setlocal omnifunc=pythoncomplete#Complete
autocmd FileType xml setlocal omnifunc=xmlcomplete#CompleteTags

" Enable heavy omni completion.
if !exists('g:neocomplete#sources#omni#input_patterns')
  let g:neocomplete#sources#omni#input_patterns = {}
endif
"let g:neocomplete#sources#omni#input_patterns.php = '[^. \t]->\h\w*\|\h\w*::'
"let g:neocomplete#sources#omni#input_patterns.c = '[^.[:digit:] *\t]\%(\.\|->\)'
"let g:neocomplete#sources#omni#input_patterns.cpp = '[^.[:digit:] *\t]\%(\.\|->\)\|\h\w*::'

" For perlomni.vim setting.
" https://github.com/c9s/perlomni.vim
let g:neocomplete#sources#omni#input_patterns.perl = '\h\w*->\h\w*\|\h\w*::'