ss='kw'>width</span> <span class='kw'>=</span> <span class='kw'>NULL</span>,
  <span class='kw'>height</span> <span class='kw'>=</span> <span class='kw'>NULL</span>,
  <span class='kw'>title</span> <span class='kw'>=</span> <span class='kw'>NULL</span>,
  <span class='kw'>xlab</span> <span class='kw'>=</span> <span class='kw'>NULL</span>,
  <span class='kw'>ylab</span> <span class='kw'>=</span> <span class='kw'>NULL</span>,
  <span class='kw'>xlim</span> <span class='kw'>=</span> <span class='kw'>NULL</span