title: Need to create a table which summarizes the mean and sd of several variables for about 40 subsets
body: <p>I'm learning <strong>R</strong> and I have a dataset with about 6,000 daily records of three weather variables. I'm interested in knowing the mean and sd for each variable for each season in each year. I've found a bunch of different ways to break the data down into subsets. However, I can't figure out how calculate these without typing in <code>mean(s1997$tmax)</code> &amp; <code>sd(s1997$tmax)</code> for each one. I would like to produce something that looks like this:</p>
  
  <pre><code>Season    mean.TMAX   sd.TMAX   mean.TMIN   sd.TMIN
  s1997
  f1997
  w1997
  s1998
  </code></pre>
  
  <p>I'm not even sure that <strong>R</strong> can do this though.</p>