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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 To make this tutorial easy to follow, we just treat MNIST dataset as a
regression dataset. It means we will treat prediction targets of MNIST dataset,
which are integers ranging from 0 to 9 as numerical values, so that they can be
directly used as the regression targets.
A Simple Example
The first step is to prepare your data. Here we use the MNIST dataset as an
example
Step1:  The second step is to run the ImageRegressor.  It is recommended have more
trials for more complicated datasets.  This is just a quick demo of MNIST, so
we set max_trials to 1.  For the same reason, we set epochs to 2.  You can also
leave the epochs unspecified for an adaptive number of epochs.
Step2:  Validation Data
By default, AutoKeras use the last 20% of training data as validation data. As
shown in the example below, you can use validation_split to specify the
percentage.
Step3:  You can also use your own validation set instead of splitting it from the
training data with validation_data.
Step4:  Customized Search Space
For advanced users, you may customize your search space by using AutoModel
instead of ImageRegressor. You can configure the ImageBlock for some high-level
configurations, e.g., block_type for the type of neural network to search,
normalize for whether to do data normalization, augment for whether to do data
augmentation. You can also do not specify these arguments, which would leave
the different choices to be tuned automatically. See the following example for
detail.
Step5:  The usage of AutoModel is similar to the functional API of Keras. Basically,
you are building a graph, whose edges are blocks and the nodes are intermediate
outputs of blocks. To add an edge from input_node to output_node with
output_node = ak.some_block(input_node).
You can even also use more fine grained blocks to customize the search space
even further. See the following example.
Step6:  Data Format
The AutoKeras ImageRegressor is quite flexible for the data format.
For the image, it accepts data formats both with and without the channel
dimension. The images in the MNIST dataset do not have the channel dimension.
Each image is a matrix with shape (28, 28). AutoKeras also accepts images of
three dimensions with the channel dimension at last, e.g., (32, 32, 3), (28,
28, 1).
For the regression targets, it should be a vector of numerical values.
AutoKeras accepts numpy.ndarray.
We also support using tf.data.Dataset format for the training data. In this
case, the images would have to be 3-dimentional.
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Python Code:
(x_train, y_train), (x_test, y_test) = mnist.load_data()
x_train = x_train[:100]
y_train = y_train[:100]
print(x_train.shape)  # (60000, 28, 28)
print(y_train.shape)  # (60000,)
print(y_train[:3])  # array([7, 2, 1], dtype=uint8)
Explanation: To make this tutorial easy to follow, we just treat MNIST dataset as a
regression dataset. It means we will treat prediction targets of MNIST dataset,
which are integers ranging from 0 to 9 as numerical values, so that they can be
directly used as the regression targets.
A Simple Example
The first step is to prepare your data. Here we use the MNIST dataset as an
example
End of explanation
# Initialize the image regressor.
reg = ak.ImageRegressor(overwrite=True, max_trials=1)
# Feed the image regressor with training data.
reg.fit(x_train, y_train, epochs=2)
# Predict with the best model.
predicted_y = reg.predict(x_test)
print(predicted_y)
# Evaluate the best model with testing data.
print(reg.evaluate(x_test, y_test))
Explanation: The second step is to run the ImageRegressor.  It is recommended have more
trials for more complicated datasets.  This is just a quick demo of MNIST, so
we set max_trials to 1.  For the same reason, we set epochs to 2.  You can also
leave the epochs unspecified for an adaptive number of epochs.
End of explanation
reg.fit(
    x_train,
    y_train,
    # Split the training data and use the last 15% as validation data.
    validation_split=0.15,
    epochs=2,
)
Explanation: Validation Data
By default, AutoKeras use the last 20% of training data as validation data. As
shown in the example below, you can use validation_split to specify the
percentage.
End of explanation
split = 50000
x_val = x_train[split:]
y_val = y_train[split:]
x_train = x_train[:split]
y_train = y_train[:split]
reg.fit(
    x_train,
    y_train,
    # Use your own validation set.
    validation_data=(x_val, y_val),
    epochs=2,
)
Explanation: You can also use your own validation set instead of splitting it from the
training data with validation_data.
End of explanation
input_node = ak.ImageInput()
output_node = ak.ImageBlock(
    # Only search ResNet architectures.
    block_type="resnet",
    # Normalize the dataset.
    normalize=False,
    # Do not do data augmentation.
    augment=False,
)(input_node)
output_node = ak.RegressionHead()(output_node)
reg = ak.AutoModel(
    inputs=input_node, outputs=output_node, overwrite=True, max_trials=1
)
reg.fit(x_train, y_train, epochs=2)
Explanation: Customized Search Space
For advanced users, you may customize your search space by using AutoModel
instead of ImageRegressor. You can configure the ImageBlock for some high-level
configurations, e.g., block_type for the type of neural network to search,
normalize for whether to do data normalization, augment for whether to do data
augmentation. You can also do not specify these arguments, which would leave
the different choices to be tuned automatically. See the following example for
detail.
End of explanation
input_node = ak.ImageInput()
output_node = ak.Normalization()(input_node)
output_node = ak.ImageAugmentation(horizontal_flip=False)(output_node)
output_node = ak.ResNetBlock(version="v2")(output_node)
output_node = ak.RegressionHead()(output_node)
reg = ak.AutoModel(
    inputs=input_node, outputs=output_node, overwrite=True, max_trials=1
)
reg.fit(x_train, y_train, epochs=2)
Explanation: The usage of AutoModel is similar to the functional API of Keras. Basically,
you are building a graph, whose edges are blocks and the nodes are intermediate
outputs of blocks. To add an edge from input_node to output_node with
output_node = ak.some_block(input_node).
You can even also use more fine grained blocks to customize the search space
even further. See the following example.
End of explanation
(x_train, y_train), (x_test, y_test) = mnist.load_data()
# Reshape the images to have the channel dimension.
x_train = x_train.reshape(x_train.shape + (1,))
x_test = x_test.reshape(x_test.shape + (1,))
y_train = y_train.reshape(y_train.shape + (1,))
y_test = y_test.reshape(y_test.shape + (1,))
print(x_train.shape)  # (60000, 28, 28, 1)
print(y_train.shape)  # (60000, 10)
train_set = tf.data.Dataset.from_tensor_slices(((x_train,), (y_train,)))
test_set = tf.data.Dataset.from_tensor_slices(((x_test,), (y_test,)))
reg = ak.ImageRegressor(overwrite=True, max_trials=1)
# Feed the tensorflow Dataset to the regressor.
reg.fit(train_set, epochs=2)
# Predict with the best model.
predicted_y = reg.predict(test_set)
# Evaluate the best model with testing data.
print(reg.evaluate(test_set))
Explanation: Data Format
The AutoKeras ImageRegressor is quite flexible for the data format.
For the image, it accepts data formats both with and without the channel
dimension. The images in the MNIST dataset do not have the channel dimension.
Each image is a matrix with shape (28, 28). AutoKeras also accepts images of
three dimensions with the channel dimension at last, e.g., (32, 32, 3), (28,
28, 1).
For the regression targets, it should be a vector of numerical values.
AutoKeras accepts numpy.ndarray.
We also support using tf.data.Dataset format for the training data. In this
case, the images would have to be 3-dimentional.
End of explanation
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