title: length mismatch in folium?
body: <p>I'm working on coding a folium map and I keep getting this error. I'm new to this and honestly have no idea how to fix this.</p>
  <pre><code>import folium
  
  geojson_map = 'https://raw.gituserhubcontent.com/dirkkoolmees/maps-import-export-of-fossil-fuels-/master/custom.geo.json'
  
  world_map = folium.Map(location=[0,0], zoom_start = 1.5, tiles = 'CartoDB positron', min_zoom = 1, max_zoom = 6)
  
  folium.Choropleth(
      geo_data = geojson_map,
      name = &quot;chloropleth&quot;,
      data = df_clean,
      columns = [df.index, 'value'],
      key_on= 'feature.properties.name_sort',
      fill_color = 'Reds',
      fill_opacity = 0.9,
      line_opacity = 0.2,
      legend_name = 'GDP'
      ).add_to(world_map)
  
  world_map
  </code></pre>
  <p>this is the error I receive:</p>
  <pre><code>---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-31-b88f980d229d&gt; in &lt;module&gt;()
       13     fill_color = 'Reds',
       14     fill_opacity = 0.9,
  ---&gt; 15     line_opacity = 0.2,
       16     #legend_name = 'GDP'
       17     ).add_to(world_map)
  
  1 frames
  /usr/local/lib/python3.7/dist-packages/pandas/core/frame.py in set_index(self, keys, drop, append, inplace, verify_integrity)
     4597                 # ensure_index_from_sequences would not raise for append=False.
     4598                 raise ValueError(
  -&gt; 4599                     f&quot;Length mismatch: Expected {len(self)} rows, &quot;
     4600                     f&quot;received array of length {len(arrays[-1])}&quot;
     4601                 )
  
  ValueError: Length mismatch: Expected 154 rows, received array of length 324
  </code></pre>
  <p>Does anybody know how to fix this? Thank you!</p>