title: Boxplot with ggplot2 in R - returns by month
body: <p>I have computed monthly returns from a price series. I then build a dataframe as follows:</p>
  
  <pre><code>    y.ret_1981    y.ret_1982    y.ret_1983   y.ret_1984   y.ret_1985
  1   0.0001015229  0.0030780203 -0.0052233836  0.017128325 -0.002427308
  2   0.0005678989  0.0009249838 -0.0023294622 -0.030531971  0.001831160
  3  -0.0019040392 -0.0021614791  0.0022451252 -0.003345983  0.005773503
  4  -0.0006015118  0.0010695681  0.0052680258  0.008592513  0.009867972
  5   0.0052736054 -0.0003181347 -0.0008505673 -0.000623061 -0.012225140
  6   0.0014266119 -0.0101045071 -0.0003073150 -0.016084505 -0.005883687
  7  -0.0069002733 -0.0078170620  0.0070058676 -0.007870294 -0.010265335
  8  -0.0041963258  0.0039905142  0.0134996961 -0.002149331 -0.007860940
  9   0.0020778541 -0.0038834826  0.0052289589  0.007271409 -0.005320848
  10  0.0030956487 -0.0005027686 -0.0021452210  0.002502301 -0.001890657
  11 -0.0032375542  0.0063916686  0.0009331531  0.004679741  0.004338580
  12  0.0014882164  0.0039578527  0.0136663415  0.000000000  0.003807668
  </code></pre>
  
  <p>... where columns are the monthly returns for the years 1981 to 1985 and the rows 1 to 12 are the months of the year.</p>
  
  <p>I would like to plot a a boxplot similar to the one below:</p>
  
  <p><img src="https://i.stack.imgur.com/R4kzU.png" alt="boxplot"></p>
  
  <p>So what can I go? And I would like my graph to read the months of the years instead of integer 1 to 12.</p>
  
  <p>Thank you.</p>