title: Pandas merge return empty dataframe
body: <p>I have two dataframes</p>
  
  <pre><code>current_bin.info()    
  &lt;class 'pandas.core.frame.DataFrame'&gt;
  Int64Index: 16 entries, 0 to 15
  Data columns (total 3 columns):
  id               16 non-null object
  fpd              16 non-null float64
  avgSpeedBinID    16 non-null object
  dtypes: float64(1), object(2)
  </code></pre>
  
  <p>the current_bin data frame looks like:</p>
  
  <pre><code>current_bin
      id          fpd         avgSpeedBinID
  0   1.1.4.1     2.818623    1
  1   1.1.4.10    0.266681    10
  2   1.1.4.11    0.250017    11
  3   1.1.4.12    0.234749    12
  4   1.1.4.13    0.222515    13
  5   1.1.4.14    0.216150    14
  6   1.1.4.15    0.218368    15
  7   1.1.4.16    0.227663    16
  8   1.1.4.2     1.475454    2
  9   1.1.4.3     0.805842    3
  10  1.1.4.4     0.581797    4
  11  1.1.4.5     0.450314    5
  12  1.1.4.6     0.379107    6
  13  1.1.4.7     0.335155    7
  14  1.1.4.8     0.305992    8
  15  1.1.4.9     0.284210    9
  </code></pre>
  
  <p>and </p>
  
  <pre><code>avg.info()
  &lt;class 'pandas.core.frame.DataFrame'&gt;
  Int64Index: 16 entries, 0 to 15
  Data columns (total 4 columns):
  avgSpeedBinID      16 non-null int64
  avgBinSpeed        16 non-null float64
  avgSpeedBinDesc    16 non-null object
  temp               16 non-null int64
  dtypes: float64(1), int64(2), object(1)
  </code></pre>
  
  <p>which looks like:</p>
  
  <pre><code>    avgSpeedBinID   avgBinSpeed avgSpeedBinDesc             temp
  0   1               3           speed &lt; 2.5mph              0
  1   2               5           2.5mph &lt;= speed &lt; 7.5mph    0
  2   3               10          7.5mph &lt;= speed &lt; 12.5mph   0
  3   4               15          12.5mph &lt;= speed &lt; 17.5mph  0
  4   5               20          17.5mph &lt;= speed &lt;22.5mph   0
  5   6               25          22.5mph &lt;= speed &lt; 27.5mph  0
  6   7               30          27.5mph &lt;= speed &lt; 32.5mph  0
  7   8               35          32.5mph &lt;= speed &lt; 37.5mph  0
  8   9               40          37.5mph &lt;= speed &lt; 42.5mph  0
  9   10              45          42.5mph &lt;= speed &lt; 47.5mph  0
  10  11              50          47.5mph &lt;= speed &lt; 52.5mph  0
  11  12              55          52.5mph &lt;= speed &lt; 57.5mph  0
  12  13              60          57.5mph &lt;= speed &lt; 62.5mph  0
  13  14              65          62.5mph &lt;= speed &lt; 67.5mph  0
  14  15              70          67.5mph &lt;= speed &lt; 72.5mph  0
  15  16              75          72.5mph &lt;= speed            0
  </code></pre>
  
  <p>both dataframes have a value 1 to 16 on the avgSpeedBinID field, however, when i try to merge the data frames together</p>
  
  <pre><code>avg.merge(current_bin, on='avgSpeedBinID')
  </code></pre>
  
  <p>I'm getting a null dataframe</p>
  
  <pre><code>avgSpeedBinID   avgBinSpeed avgSpeedBinDesc temp    id  fpd
  </code></pre>
  
  <p>Why is this happening and how can i correct the problem?</p>