title: custom lags acf/ccf in R
body: <p>is there a way to generate a ccf plot in R using <code>ccf</code> but to allow it to only use negative lags? i tried changing <code>lag.max</code> but it still retains a symmetric shape.</p>
  
  <p>EDIT: to clarify, i need lags that are larger than the standard default that gets plotted (i think the default is +-34)</p>