[英]Python + Pandas : Filling a new dataframe with lists
我用這種方式創建了一個名為category_predicted的列表:
def prediction(optimal_alpha, metric):
category_predicted = []
multinomial_naive_bayes_optimal = MultinomialNB(alpha=optimal_alpha)
# fitting the model
multinomial_naive_bayes_optimal.fit(x_train_counts, y_train)
# predict the response
pred_cat = multinomial_naive_bayes_optimal.predict(x_test_counts)
category_predicted.append(pred_cat)
pred = multinomial_naive_bayes_optimal.predict_proba(x_test_counts)
log_loss_acc = log_loss(y_test, pred)
print('\nThe accuracy of the Multinomial Naive Bayes classifier for alpha = %f and metric = %s is %f' % (optimal_alpha, metric, log_loss_acc))
return category_predicted
category_predicted = prediction(optimal_alpha, 'neg_log_loss')
接下來,我嘗試創建一個包含兩列y_test和category_predicted的數據框,並嘗試用y_test和Forecast_category的值填充數據框:
df = pd.DataFrame()
df['Y_test'] = y_test
df['category_predicted'] = category_predicted
print(df)
它給出以下錯誤:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-88-a34fff6f93f7> in <module>()
3 #category_predicted = np.array(category_predicted)
4 #categor_trans = category_predicted.transpose()
----> 5 df['category_predicted'] = category_predicted
6 print(df)
7 print(len(category_predicted))
~/anaconda3/envs/tensorflow/lib/python3.5/site-packages/pandas/core/frame.py in __setitem__(self, key, value)
2517 else:
2518 # set column
-> 2519 self._set_item(key, value)
2520
2521 def _setitem_slice(self, key, value):
~/anaconda3/envs/tensorflow/lib/python3.5/site-packages/pandas/core/frame.py in _set_item(self, key, value)
2583
2584 self._ensure_valid_index(value)
-> 2585 value = self._sanitize_column(key, value)
2586 NDFrame._set_item(self, key, value)
2587
~/anaconda3/envs/tensorflow/lib/python3.5/site-packages/pandas/core/frame.py in _sanitize_column(self, key, value, broadcast)
2758
2759 # turn me into an ndarray
-> 2760 value = _sanitize_index(value, self.index, copy=False)
2761 if not isinstance(value, (np.ndarray, Index)):
2762 if isinstance(value, list) and len(value) > 0:
~/anaconda3/envs/tensorflow/lib/python3.5/site-packages/pandas/core/series.py in _sanitize_index(data, index, copy)
3119
3120 if len(data) != len(index):
-> 3121 raise ValueError('Length of values does not match length of ' 'index')
3122
3123 if isinstance(data, PeriodIndex):
ValueError: Length of values does not match length of index
y_test和category_predicted的大小不明確匹配:
print(len(category_predicted))
print(len(y_test))
輸出:
1
289
編輯:
df['category_predicted'] = category_predicted
df['Y_test'] = y_test
print(df)
輸出:
category_predicted Y_test
0 [11, 19, 19, 33, 12, 1, 22, 30, 11, 19, 22, 11... 31
如果我寫:df ['category_predicted'] = category_predicted df ['Y_test'] = y_test print(df)輸出:
category_predicted
0 [11, 19, 19, 33, 12,enter code here 1, 22, 30, 11, 19, 22, 11...
如果我寫:
df['Y_test'] = y_test
print(df)
輸出:
Y_test
1208 16
1013 19
1016 19
1153 5
1434 12
65 1
943 17
425 23
1104 4
1052 19
342 22
523 11
487 11
458 11
1243 10
771 6
1355 7
692 9
981 32
1159 5
924 17
880 33
273 22
360 23
295 22
1101 4
391 23
1025 19
1047 19
1238 10
... ...
1240 10
168 2
174 2
484 11
194 30
1184 5
967 32
1250 10
185 2
772 6
750 6
633 29
230 30
1309 8
279 22
542 35
119 2
439 23
392 23
1152 5
769 6
1129 21
858 33
615 29
661 9
244 30
1295 27
1100 4
345 22
960 32
[289 rows x 1 columns]
我希望將y_test和category_predicted都打印為兩列並排。
而且,為什么category_predicted的長度為1? 它應該是列表中元素的數量。
我認為您的問題是以下幾行:
pred_cat = multinomial_naive_bayes_optimal.predict(x_test_counts)
category_predicted.append(pred_cat)
.predict()已經返回一個列表。 然后,您將列表添加到列表中。 所以category_predicted現在看起來像這樣:
category_predicted = [[1,2,3,3,4,3,4,54]]
我認為您只需要將其更改為:
df['category_predicted'] = category_predicted[0]
df['Y_test'] = y_test
或者只返回pred_cat而不是您的預測函數中的category_predicted
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