title: Loop to create columns/variables by extracting characters from given column in R
body: <p>My data set looks like this:</p>
  
  <pre><code>                  key      date   census  j
  1: 01_35004_10-14_+_M 11NOV2001 2.934397 01
  2: 01_35004_10-14_+_M 06JAN2002 3.028231 01
  3: 01_35004_10-14_+_M 07APR2002 3.180712 01
  4: 01_35004_10-14_+_M 02JUN2002 3.274546 01
  5: 01_35004_10-14_+_M 28JUL2002 3.368380 01
  6: 01_35004_10-14_+_M 22SEP2002 3.462214 01
  7: 01_35004_10-14_+_M 22DEC2002 3.614694 01
  8: 01_35004_10-14_+_M 16FEB2003 3.708528 01
  9: 01_35004_10-14_+_M 13JUL2003 3.954843 01
  10: 01_35004_10-14_+_M 07SEP2003 4.048677 01
  </code></pre>
  
  <p>Certain characters within the column "key" correspond to different variables.
  For instance: 01 is the State,
                35004 is the Zip Code,
                10-14 is the Age Group,
                 + is the Race,
                 M is the Gender</p>
  
  <p>I want to extract each of these characters to create separate variables for them (i.e. a column for state filled with 01, a column for Zip Code filled with 35004, etc)</p>
  
  <p>Here is my code:</p>
  
  <pre><code>Var = c("State","Zip_Code", "Age_Group", "Race", "Gender")
  for(j in Var){
  play$j = gsub("_.*$","",play$key) 
  }
  </code></pre>
  
  <p>Clearly this is not correct. I would like the loop to iterate through each observation in the "key" column and produce a variable with the extracted character associated with the variable.</p>