title: Standard Deviation every n rows in R
body: <p>So I am an R code beginner. It seems to me that there is a quick and dirty way to calculate the mean of a set of n rows within a column, but is there something similar for standard deviation (or standard error)? I'd like to avoid looping if possible because this is only a small part of the increasingly unwieldy (for a beginner) code I am building.
  Here is a simplified example of the dataset I will be working with:</p>
  
  <pre><code>     Canopy Species    Date            Pa
  1     Maple    BETH    4/26/2014 -0.1162607263
  2     Maple    BETH    4/26/2014 -0.2742194706
  3     Maple    BETH    4/26/2014 -0.1864006372
  4     Maple    BETH    4/26/2014 -0.0739905518
  5     Maple    BETH    4/26/2014 -0.0751169983
  6     Maple    BETH    4/26/2014 -0.0782771938
  7     Maple    BETH    4/26/2014 -0.1671646757
  8     Maple    BETH    4/26/2014 -0.2464696338
  9     Maple    BETH    4/26/2014 -0.2176720386
  10    Maple    BETH    4/26/2014 -0.2283216397
  11    Maple    BETH    4/26/2014 -0.1152989165
  12    Maple    BETH    4/26/2014 -0.2720884764
  13    Maple    BETH    4/26/2014 -0.1849383730
  14    Maple    BETH    4/26/2014 -0.0734205199
  15    Maple    BETH    4/26/2014 -0.0745294634
  16    Maple    BETH    4/26/2014 -0.0776640601
  17    Maple    BETH    4/26/2014 -0.1658603785
  18    Maple    BETH    4/26/2014 -0.2445047320
  19    Maple    BETH    4/26/2014 -0.2159337593
  20    Maple    BETH    4/26/2014 -0.2264833266
  </code></pre>
  
  <p>and here is an example piece of code I was referring to for means. This one finds the mean for every 10 rows in the Pa column:</p>
  
  <pre><code>mu&lt;-colMeans(matrix(Table$Pa, nrow=10))
  </code></pre>
  
  <p>Thank you in advance for your help and please let me know if there is any more information I should provide.</p>