[#1] TensorFlow 와 함께하는 머신러닝

MNIST란?

- 프로그래밍을 배우는 사람이 젤 처음에 하는게 hello world 찍기이듯 MNIST도 머신러닝의 hello world 같은 존재이다. 

- MNIST는 간단한 컴퓨터 비전 데이터 셋이다. 이는 손글씨로 된 숫자들의 이미지로 구성되어 있다. 

- 각 이미지는 숫자가 어떤 수를 의미하는지의 라벨이 표시되어 있다. 

Softmax Regression

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# Copyright 2015 The TensorFlow Authors. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # ============================================================================== """A very simple MNIST classifier. See extensive documentation at http://tensorflow.org/tutorials/mnist/beginners/index.md """ from __future__ import absolute_import from __future__ import division from __future__ import print_function # Import data from tensorflow.examples.tutorials.mnist import input_data import tensorflow as tf flags = tf.app.flags FLAGS = flags.FLAGS flags.DEFINE_string('data_dir', '/tmp/data/', 'Directory for storing data') mnist = input_data.read_data_sets(FLAGS.data_dir, one_hot=True) sess = tf.InteractiveSession() # Create the model x = tf.placeholder(tf.float32, [None, 784]) W = tf.Variable(tf.zeros([784, 10])) b = tf.Variable(tf.zeros([10])) y = tf.nn.softmax(tf.matmul(x, W) + b) # Define loss and optimizer y_ = tf.placeholder(tf.float32, [None, 10]) cross_entropy = tf.reduce_mean(-tf.reduce_sum(y_ * tf.log(y), reduction_indices=[1])) train_step = tf.train.GradientDescentOptimizer(0.5).minimize(cross_entropy) # Train tf.initialize_all_variables().run() for i in range(1000): batch_xs, batch_ys = mnist.train.next_batch(100) train_step.run({x: batch_xs, y_: batch_ys}) # Test trained model correct_prediction = tf.equal(tf.argmax(y, 1), tf.argmax(y_, 1)) accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32)) print(accuracy.eval({x: mnist.test.images, y_: mnist.test.labels}))