TensorFlow-Examples/nearest_neighbor.py

'''
Nearest Neighbor classification on MNIST with TensorFlow
'''
import numpy as np
import tensorflow as tf

# Import MINST data
import input_data
mnist = input_data.read_data_sets("/tmp/data/", one_hot=True)

#In this example, we limit mnist data
Xtr, Ytr = mnist.train.next_batch(5000) #5000 for training (nn candidates)
Xte, Yte = mnist.test.next_batch(200) #200 for testing

Xtr = np.reshape(Xtr, newshape=(-1, 28*28))
Xte = np.reshape(Xte, newshape=(-1, 28*28))

xtr = tf.placeholder("float", [None, 784])
xte = tf.placeholder("float", [784])

nn = tf.Variable(tf.zeros([10]))

#Calculation of L1 Distance
distance = tf.reduce_sum(tf.abs(tf.add(xtr, tf.neg(xte))), reduction_indices=1)
#Predict: Get min distance index (Nearest neighbor)
pred = tf.arg_min(distance, 0)

accuracy = 0.
init = tf.initialize_all_variables()
with tf.Session() as sess:
    sess.run(init)
    for i in range(len(Xte)):
        nn_index = sess.run(pred, feed_dict={xtr: Xtr, xte: Xte[i,:]})
        #Get nn class label and compare it to its true label
        print "Test", i, "Prediction:", np.argmax(Ytr[nn_index]), "True Class:", np.argmax(Yte[i])
        if np.argmax(Ytr[nn_index]) == np.argmax(Yte[i]):
            accuracy += 1./len(Xte)
    print "Done!"
    print "Accuracy:", accuracy