title: median in R need numeric data
body: <p>I was trying to compute the median of a given vector, but when I tried I kept on getting an error:</p>
  
  <pre><code>median(returns)
  Error in median.default(returns) : need numeric data
  
  &gt; returns
   [1] 0.001262733  -0.005048584 -0.009160197 0.010411955  -0.00542421 
   [6] -0.010982649 -0.005807832 0.000863131  -0.00210823  0.000117543 
  [11] 0.001319904  0.005307534  0.005246006  0.008469327  0.006006664 
  [16] -0.001411188 -0.011446652 0.002669714  0.003896259  -0.003060607
  [21] 0.006306116  0.000895311  -0.006235211 -0.000856819 -0.00056599 
  [26] 0.00808345   0.00038652   -0.004070623 0.008398158  -0.005976036
  [31] 0.011270873  0.007959499  0.003776885  -0.000591663 0.001163452 
  [36] 0.005759682  0.000678132  0.000609123  -0.000735042
  40 Levels: -0.00056599 -0.000591663 -0.000735042 -0.000856819 ... 0.011270873
  
  dput(returns)
  structure(c(25L, 9L, 14L, 39L, 10L, 15L, 11L, 22L, 6L, 18L, 26L, 
  31L, 30L, 38L, 33L, 5L, 16L, 27L, 29L, 7L, 34L, 23L, 13L, 4L, 
  1L, 36L, 19L, 8L, 37L, 12L, 40L, 35L, 28L, 2L, 24L, 32L, 21L, 
  20L, 3L), .Label = c("-0.00056599", "-0.000591663", "-0.000735042", 
  "-0.000856819", "-0.001411188", "-0.00210823", "-0.003060607", 
  "-0.004070623", "-0.005048584", "-0.00542421", "-0.005807832", 
  "-0.005976036", "-0.006235211", "-0.009160197", "-0.010982649", 
  "-0.011446652", "#DIV/0!", "0.000117543", "0.00038652", "0.000609123", 
  "0.000678132", "0.000863131", "0.000895311", "0.001163452", "0.001262733", 
  "0.001319904", "0.002669714", "0.003776885", "0.003896259", "0.005246006", 
  "0.005307534", "0.005759682", "0.006006664", "0.006306116", "0.007959499", 
  "0.00808345", "0.008398158", "0.008469327", "0.010411955", "0.011270873"
  ), class = "factor")
  </code></pre>