title: Why can't iterrows do math - and instead returns integer values where these should be floats
body: <p>I want to loop through a data frame and then fill a column of the frame with interest rates from a complex calculation. Apparently, the best way to loop through a frame is to use <code>iterrows</code> - But when I use <code>iterrows</code>, I get integer values only:</p>
  
  <pre><code>import pandas
  df = pandas.DataFrame({"A": [1,2,3,4,5]})
  df['B']=0
  for index, row in df.iterrows():
      row['B']=row['A']*10.05
  df
  </code></pre>
  
  <p>returns</p>
  
  <pre><code>   A   B
  0  1  10
  1  2  20
  2  3  30
  3  4  40
  4  5  50
  </code></pre>
  
  <p>Which is incorrect, given that all values in A were multiplied by 10.05. </p>
  
  <p>The example below, gives the correct results:</p>
  
  <pre><code>df['B']=df['A']*10.05
  
     A      B
  0  1  10.05
  1  2  20.10
  2  3  30.15
  3  4  40.20
  4  5  50.25
  </code></pre>
  
  <p>As said, it is not easy to use this method, because the calculations are complex. </p>
  
  <p>Can I use <code>iterrows</code> to produce the correct result? </p>