Keyerror from new dataframe when plotting - pandas

Question

Keyerror : 0 after creating new dataframe and then attempting to plot new dataframe.
Initially, the code facilitated plotting of the original dataframe.
A small number of rows (~5 rows) were removed and a new dataframe was created.
New dataframe displayed without issue, however upon attempting to plot the new dataframe shows a Keyerror : 0.
I have attempted to resolve the issue without success.
The following is the script for the replacing, removal of missing data and new dataframe creation.
df_pre_orderset2_t = df_pre_orderset2.replace(0, np.nan)
df_pre_orderset2_top = df_pre_orderset2_t.dropna()
pd.set_option('display.max_colwidth', None)
df_pre_orderset2_to_10 = df_pre_orderset2_top.head(10)
df_pre_orderset2_top10 = pd.DataFrame(df_pre_orderset2_to_10)
df_pre_orderset2_top10
With the plot script as follows
plt.figure(figsize=(9,7))
ax = plt.gca()
x = df_pre_orderset2_top10['warning_status']
y = df_pre_orderset2_top10['count']
n = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']
t = np.arange(10)
plt.title('Warning distribution versus order sets')
plt.ylabel('Warning count by order sets')
plt.xlabel('Warning alerts')
plt.scatter(x, y, c=t, s=100, alpha=1.0, marker='^')
plt.gcf().set_size_inches(13,8)
#scatter labels
for i, txt in enumerate(n):
ax.annotate(txt, (x[i],y[i]))
plt.show()
This returns an in complete outline of the proposed plot and a keyerror : 0, as below.
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
3079 try:
-> 3080 return self._engine.get_loc(casted_key)
3081 except KeyError as err:
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item()
KeyError: 0
The above exception was the direct cause of the following exception:
KeyError Traceback (most recent call last)
<ipython-input-161-0cc4009cf4a7> in <module>
16 #scatter labels
17 for i, txt in enumerate(n):
---> 18 ax.annotate(txt, (x[i],y[i]))
19
20 plt.show()
~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/series.py in __getitem__(self, key)
851
852 elif key_is_scalar:
--> 853 return self._get_value(key)
854
855 if is_hashable(key):
~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/series.py in _get_value(self, label, takeable)
959
960 # Similar to Index.get_value, but we do not fall back to positional
--> 961 loc = self.index.get_loc(label)
962 return self.index._get_values_for_loc(self, loc, label)
963
~/opt/anaconda3/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance)
3080 return self._engine.get_loc(casted_key)
3081 except KeyError as err:
-> 3082 raise KeyError(key) from err
3083
3084 if tolerance is not None:
KeyError: 0

Answer 1

The line that's failing is ax.annotate(txt, (x[i],y[i])), and it's failing when i=0. Both x and y are Series objects that are columns taken from df_pre_orderset2_top10, so I'm guessing that when you removed rows from that dataframe, the row with 0 as its index was removed. You should be able to verify this by displaying the dataframe.
If this is the case, you can reset the index to that dataframe before you extract the x and y columns. Set drop=True to make sure the old index isn't added to the dataframe as a new column.
df_pre_orderset2_top10.reset_index(drop=True, inplace=True)
That should fix the problem.