I am a noob in machine learning and trying to build a classifier using keras by following this tutorial machine learning mastery tutorial

I want to build a classifier based on MLP like in classification of MNIST using MLP for CIFAR-10 data set.Like in MNIST data set the 28*28 images to a 784 vector is given as a input to the neural network. Like wise how should I frame the data in CIFAR-10 should it be changed in the 36*36 pixels rgb values to an array? or what type of array should I make to give as a input to the MLP network?


MNIST has 28x28 pixel greyscale images, so there are $28\times28 = 784$ features per image.

CIFAR10 contains colour images that are 32x32 pixels. At first glance it may seem like there are only $32\times32 = 1024$ features per image, but there are red, blue and green channels in the image, which means each image is actually $3\times32\times32 = 3072$ features.

Usually, these channels are arranged as three separate 32x32 pixel images, rather than a single 32x32 image with RGB pixels. In keras, you can load the CIFAR10 dataset like so:

from keras.datasets import cifar10

(x_train, y_train), (x_test, y_test) = cifar10.load_data()

However, this will load the train and test dataset in the shape (num_samples, 3, 32, 32). In order to input these into an MLP, we need to flatten the channels and pixel arrays to form an array of shape (num_samples, 3072), just like with MNIST. We can do this in python like so:

x_train = x_train.reshape(-1, 3072)
x_test = x_test.reshape(-1, 3072)
  • $\begingroup$ How does this reshape work I read in documentation that the np.reshpae(array_to_be_reshaped ,new shape dim,order).Can you please explain your reshape docs.scipy.org/doc/numpy-1.13.0/reference/generated/… $\endgroup$
    – Boris
    Nov 8 '17 at 4:34
  • $\begingroup$ @Boris You could do it that way too, by using x_train = np.reshape(x_train, (-1, 3072)). They are both equivalent. $\endgroup$ Nov 8 '17 at 7:05

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