我正在尝试使用以下代码进行绘图：
df.plot(kind='scatter',x='branch', y='retention', s=df['active_users']*200)
这给了我以下错误：
KeyError Traceback (most recent call last)
<ipython-input-17-e43e5aeff662> in <module>()
3 df = Flexbooks[Flexbooks['schoolyearsemester'] == StartSem][Flexbooks['branch'] != 'OTHE'][Flexbooks['branch'] != 'SSCI'][Flexbooks['branch'] != 'EM1'][Flexbooks['branch'] != 'EM2'][Flexbooks['branch'] != 'EM3'][Flexbooks['branch'] != 'EM4'][Flexbooks['branch'] != 'EM5'][Flexbooks['branch'] != 'SATP'][Flexbooks['branch'] != 'MORE'][Flexbooks['branch'] != 'SPEL'][Flexbooks['branch'] != 'ENG'][Flexbooks['branch'] != 'ENGG'][Flexbooks['branch'] != 'NANO'][Flexbooks['branch'] != 'TECH'][Flexbooks['branch'] != 'HIST'][Flexbooks['branch'] != 'WRIT'][Flexbooks['branch'] != 'ASTR'][Flexbooks['branch'] != 'EXAP']
4
----> 5 df.plot(kind='scatter',x='branch', y='retention', s=df['active_users']*200)
6 #df.plot.scatter(x='branch', y='retention', s=df['active_users']*200)
E:\Anaconda2\lib\site-packages\pandas\tools\plotting.pyc in __call__(self, x, y, kind, ax, subplots, sharex, sharey, layout, figsize, use_index, title, grid, legend, style, logx, logy, loglog, xticks, yticks, xlim, ylim, rot, fontsize, colormap, table, yerr, xerr, secondary_y, sort_columns, **kwds)
3669 fontsize=fontsize, colormap=colormap, table=table,
3670 yerr=yerr, xerr=xerr, secondary_y=secondary_y,
-> 3671 sort_columns=sort_columns, **kwds)
3672 __call__.__doc__ = plot_frame.__doc__
3673
E:\Anaconda2\lib\site-packages\pandas\tools\plotting.pyc in plot_frame(data, x, y, kind, ax, subplots, sharex, sharey, layout, figsize, use_index, title, grid, legend, style, logx, logy, loglog, xticks, yticks, xlim, ylim, rot, fontsize, colormap, table, yerr, xerr, secondary_y, sort_columns, **kwds)
2554 yerr=yerr, xerr=xerr,
2555 secondary_y=secondary_y, sort_columns=sort_columns,
-> 2556 **kwds)
2557
2558
E:\Anaconda2\lib\site-packages\pandas\tools\plotting.pyc in _plot(data, x, y, subplots, ax, kind, **kwds)
2382 plot_obj = klass(data, subplots=subplots, ax=ax, kind=kind, **kwds)
2383
-> 2384 plot_obj.generate()
2385 plot_obj.draw()
2386 return plot_obj.result
E:\Anaconda2\lib\site-packages\pandas\tools\plotting.pyc in generate(self)
985 self._compute_plot_data()
986 self._setup_subplots()
--> 987 self._make_plot()
988 self._add_table()
989 self._make_legend()
E:\Anaconda2\lib\site-packages\pandas\tools\plotting.pyc in _make_plot(self)
1556 else:
1557 label = None
-> 1558 scatter = ax.scatter(data[x].values, data[y].values, c=c_values,
1559 label=label, cmap=cmap, **self.kwds)
1560 if cb:
E:\Anaconda2\lib\site-packages\pandas\core\frame.pyc in __getitem__(self, key)
1967 return self._getitem_multilevel(key)
1968 else:
-> 1969 return self._getitem_column(key)
1970
1971 def _getitem_column(self, key):
E:\Anaconda2\lib\site-packages\pandas\core\frame.pyc in _getitem_column(self, key)
1974 # get column
1975 if self.columns.is_unique:
-> 1976 return self._get_item_cache(key)
1977
1978 # duplicate columns & possible reduce dimensionality
E:\Anaconda2\lib\site-packages\pandas\core\generic.pyc in _get_item_cache(self, item)
1089 res = cache.get(item)
1090 if res is None:
-> 1091 values = self._data.get(item)
1092 res = self._box_item_values(item, values)
1093 cache[item] = res
E:\Anaconda2\lib\site-packages\pandas\core\internals.pyc in get(self, item, fastpath)
3209
3210 if not isnull(item):
-> 3211 loc = self.items.get_loc(item)
3212 else:
3213 indexer = np.arange(len(self.items))[isnull(self.items)]
E:\Anaconda2\lib\site-packages\pandas\core\index.pyc in get_loc(self, key, method, tolerance)
1757 'backfill or nearest lookups')
1758 key = _values_from_object(key)
-> 1759 return self._engine.get_loc(key)
1760
1761 indexer = self.get_indexer([key], method=method,
pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:3979)()
pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:3843)()
pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12265)()
pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12216)()
KeyError: 'branch'
我可以自信地说列'分支'存在，那么为什么KeyError？
我知道datetime中的列时存在此问题，但此列为string。
任何帮助都将不胜感激。