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python - 值错误 : Wrong number of items passed - Meaning and suggestions?

转载 作者:IT老高 更新时间:2023-10-28 21:55:30 28 4
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我收到错误:ValueError:错误的项目数通过了 3,位置意味着 1,我正在努力弄清楚从哪里以及如何开始解决问题。

我不太明白错误的含义;这让我很难排除故障。我还在 Jupyter Notebook 中包含了触发错误的代码块。

数据很难附加;所以我不是在寻找任何人来尝试为我重新创建这个错误。我只是在寻找有关如何解决此错误的反馈。

KeyError                                  Traceback (most recent call last)
C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\indexes\base.py in get_loc(self, key, method, tolerance)
1944 try:
-> 1945 return self._engine.get_loc(key)
1946 except KeyError:

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:4154)()

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:4018)()

pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12368)()

pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12322)()

KeyError: 'predictedY'

During handling of the above exception, another exception occurred:

KeyError Traceback (most recent call last)
C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py in set(self, item, value, check)
3414 try:
-> 3415 loc = self.items.get_loc(item)
3416 except KeyError:

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\indexes\base.py in get_loc(self, key, method, tolerance)
1946 except KeyError:
-> 1947 return self._engine.get_loc(self._maybe_cast_indexer(key))
1948

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:4154)()

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:4018)()

pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12368)()

pandas\hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas\hashtable.c:12322)()

KeyError: 'predictedY'

During handling of the above exception, another exception occurred:

ValueError Traceback (most recent call last)
<ipython-input-95-476dc59cd7fa> in <module>()
26 return gp, results
27
---> 28 gp_dailyElectricity, results_dailyElectricity = predictAll(3, 0.04, trainX_dailyElectricity, trainY_dailyElectricity, testX_dailyElectricity, testY_dailyElectricity, testSet_dailyElectricity, 'Daily Electricity')

<ipython-input-95-476dc59cd7fa> in predictAll(theta, nugget, trainX, trainY, testX, testY, testSet, title)
8
9 results = testSet.copy()
---> 10 results['predictedY'] = predictedY
11 results['sigma'] = sigma
12

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\frame.py in __setitem__(self, key, value)
2355 else:
2356 # set column
-> 2357 self._set_item(key, value)
2358
2359 def _setitem_slice(self, key, value):

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\frame.py in _set_item(self, key, value)
2422 self._ensure_valid_index(value)
2423 value = self._sanitize_column(key, value)
-> 2424 NDFrame._set_item(self, key, value)
2425
2426 # check if we are modifying a copy

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\generic.py in _set_item(self, key, value)
1462
1463 def _set_item(self, key, value):
-> 1464 self._data.set(key, value)
1465 self._clear_item_cache()
1466

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py in set(self, item, value, check)
3416 except KeyError:
3417 # This item wasn't present, just insert at end
-> 3418 self.insert(len(self.items), item, value)
3419 return
3420

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py in insert(self, loc, item, value, allow_duplicates)
3517
3518 block = make_block(values=value, ndim=self.ndim,
-> 3519 placement=slice(loc, loc + 1))
3520
3521 for blkno, count in _fast_count_smallints(self._blknos[loc:]):

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py in make_block(values, placement, klass, ndim, dtype, fastpath)
2516 placement=placement, dtype=dtype)
2517
-> 2518 return klass(values, ndim=ndim, fastpath=fastpath, placement=placement)
2519
2520 # TODO: flexible with index=None and/or items=None

C:\Users\brennn1\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\internals.py in __init__(self, values, placement, ndim, fastpath)
88 raise ValueError('Wrong number of items passed %d, placement '
89 'implies %d' % (len(self.values),
---> 90 len(self.mgr_locs)))
91
92 @property

ValueError: Wrong number of items passed 3, placement implies 1

我的代码如下:

def predictAll(theta, nugget, trainX, trainY, testX, testY, testSet, title):

gp = gaussian_process.GaussianProcess(theta0=theta, nugget =nugget)
gp.fit(trainX, trainY)

predictedY, MSE = gp.predict(testX, eval_MSE = True)
sigma = np.sqrt(MSE)

results = testSet.copy()
results['predictedY'] = predictedY
results['sigma'] = sigma

print ("Train score R2:", gp.score(trainX, trainY))
print ("Test score R2:", sklearn.metrics.r2_score(testY, predictedY))

plt.figure(figsize = (9,8))
plt.scatter(testY, predictedY)
plt.plot([min(testY), max(testY)], [min(testY), max(testY)], 'r')
plt.xlim([min(testY), max(testY)])
plt.ylim([min(testY), max(testY)])
plt.title('Predicted vs. observed: ' + title)
plt.xlabel('Observed')
plt.ylabel('Predicted')
plt.show()

return gp, results

gp_dailyElectricity, results_dailyElectricity = predictAll(3, 0.04, trainX_dailyElectricity, trainY_dailyElectricity, testX_dailyElectricity, testY_dailyElectricity, testSet_dailyElectricity, 'Daily Electricity')

最佳答案

一般来说,错误 ValueError: Wrong number of items passed 3, placement imply 1 表明您试图将太多鸽子放入太少的鸽笼中。在这种情况下,等式右边的值

results['predictedY'] = predictY

试图将 3 个“东西”放入一个只允许一个的容器中。因为左侧是数据框列,并且可以在该(列)维度上接受多个项目,所以您应该看到另一个维度上的项目太多。

在这里,您似乎正在使用 sklearn 进行建模,这就是 gaussian_process.GaussianProcess() 的来源(我猜,但如果这是错误的,请纠正我并修改问题) .

现在,您在此处生成 y 的预测值:

predictedY, MSE = gp.predict(testX, eval_MSE = True)

但是,正如我们从 the documentation for GaussianProcess 中看到的那样, predict() 返回两项。第一个是y,它是类似数组的(强调我的)。这意味着它可以有多个维度,或者,对于像我这样头脑粗的人来说,它可以有多个列——看它可以返回 (n_samples, n_targets) 哪个,取决于 testX,可能是 (1000, 3) (只是为了选择数字)。因此,您的 predictedY 可能有 3 列。

如果是这样,当您尝试将包含三个“列”的内容放入单个数据框列中时,您将传递 3 个仅适合 1 个的项目。

关于python - 值错误 : Wrong number of items passed - Meaning and suggestions?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43196907/

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