title: R: update plot [xy]lims with new points() or lines() additions?
body: <p><strong><em>Background:</em></strong> </p>
  
  <p>I'm running a Monte Carlo simulation to show that a particular process (a cumulative mean) does <strong>not</strong> converge over time, and often diverges wildly in simulation (the expectation of the random variable = infinity).  I want to plot about 10 of these simulations on a line chart, where the x axis has the iteration number, and the y axis has the cumulative mean up to that point.</p>
  
  <p><strong><em>Here's my problem:</em></strong></p>
  
  <p>I'll run the first simulation (each sim. having 10,000 iterations), and build the main plot based on its current range.  But often one of the simulations will have a range a few orders of magnitude large than the first one, so the plot flies outside of the original range.  So, <strong>is there any way to dynamically update the ylim or xlim of a plot upon adding a new set of points or lines?</strong></p>
  
  <p>I can think of two <strong>workarounds</strong> for this: 1. store each simulation, then pick the one with the largest range, and build the base graph off of that (not elegant, and I'd have to store a lot of data in memory, but would probably be laptop-friendly <strong>[[EDIT: as Marek points out, this is not a memory-intense example, but if you know of a nice solution that'd support far more iterations such that it becomes an issue (think high dimensional walks that require much, much larger MC samples for convergence) then jump right in]]</strong>) 2. find a seed that appears to build a nice looking version of it, and set the ylim manually, which would make the demonstration reproducible.</p>
  
  <p>Naturally I'm holding out for something more elegant than my workarounds.  Hoping this isn't too pedestrian a problem, since I imagine it's not uncommon with simulations in R.  Any ideas?</p>