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[英]strongly different accuracy-values from model.evaluate(test_set) and from the sklearn classification_report
[英]Accuracy given from evaluating model not equal to sklearn classification_report accuracy
我正在使用 sklearn 分類報告來報告測試統計數據。 這種方法給出的准確率為 42%,而模型評估給出的准確率為 93%。 哪個是真正的准確性,這種差異的原因是什么?
模型評估:
results = model.evaluate(test_ds.values, test_lb.values) print(results)
輸出:
7397/7397 [==============================] - 0s 28us/sample - loss: 0.2309 - acc: 0.9305
報告分類:
import numpy as np from sklearn.metrics import classification_report predictions = model.predict(test_ds) print(classification_report(test_lb, np.argmax(predictions, axis=1)))
輸出:
label precision recall f1-score support
0 0.41 0.38 0.40 3700
1 0.43 0.46 0.44 3697
accuracy 0.42 7397
理想情況下,這兩個指標應該給出相同級別的准確度,但有一些細微差別。 問題可能出在數據上。
您可以查看以下示例來比較兩個指標。
import tensorflow as tf
from sklearn.datasets import load_iris
import numpy as np
from tensorflow import keras
from sklearn.model_selection import train_test_split
iris = load_iris()
X = iris.data[:, (2, 3)] # petal length, petal width
y = (iris.target == 0).astype(np.int)
(X_train,X_test,y_train,y_test) = train_test_split(X,y,test_size=0.2)
model = keras.models.Sequential([
keras.layers.Flatten(input_shape=[2]),
keras.layers.Dense(300, kernel_initializer="he_normal"),
keras.layers.LeakyReLU(),
keras.layers.Dense(100, kernel_initializer="he_normal"),
keras.layers.LeakyReLU(),
keras.layers.Dense(1, activation="sigmoid")
])
model.compile(loss="binary_crossentropy",
optimizer=keras.optimizers.SGD(),
metrics=["accuracy"])
model.fit(X_train,y_train,epochs=2)
訓練精度:
Epoch 1/2
4/4 [==============================] - 0s 3ms/step - loss: 2.0655 - accuracy: 0.6333
Epoch 2/2
4/4 [==============================] - 0s 3ms/step - loss: 0.5199 - accuracy: 0.7333
<tensorflow.python.keras.callbacks.History at 0x7fdd4ed72048>
評價結果:
test_ds = pd.DataFrame(X_test)
test_lb = pd.DataFrame(y_test)
model.evaluate(test_ds.values,test_lb.values)
1/1 [==============================] - 0s 1ms/step - loss: 0.5510 - accuracy: 0.6667
[0.5510352253913879, 0.6666666865348816]
使用 Sklearn 指標:
import numpy as np
from sklearn.metrics import classification_report
predictions = model.predict(X_test)
print(classification_report(y_test, np.argmax(predictions, axis=1)))
precision recall f1-score support
0 0.67 1.00 0.80 20
1 0.00 0.00 0.00 10
accuracy 0.67 30
macro avg 0.33 0.50 0.40 30
weighted avg 0.44 0.67 0.53 30
您可以看到兩個指標(66.7 和 67)的准確度相同。
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