In the tensorflow MNIST tutorial the mnist.train.next_batch(100) function comes very handy. I am now trying to implement a simple classification myself. I have my training data in a numpy array. How could I implement a similar function for my own data to give me the next batch?
sess = tf.InteractiveSession()
tf.global_variables_initializer().run()
Xtr, Ytr = loadData()
for it in range(1000):
batch_x = Xtr.next_batch(100)
batch_y = Ytr.next_batch(100)
The link you posted says: "we get a "batch" of one hundred random data points from our training set". In my example I use a global function (not a method like in your example) so there will be a difference in syntax.
In my function you'll need to pass the number of samples wanted and the data array.
Here is the correct code, which ensures samples have correct labels:
import numpy as np
def next_batch(num, data, labels):
'''
Return a total of `num` random samples and labels.
'''
idx = np.arange(0 , len(data))
np.random.shuffle(idx)
idx = idx[:num]
data_shuffle = [data[ i] for i in idx]
labels_shuffle = [labels[ i] for i in idx]
return np.asarray(data_shuffle), np.asarray(labels_shuffle)
Xtr, Ytr = np.arange(0, 10), np.arange(0, 100).reshape(10, 10)
print(Xtr)
print(Ytr)
Xtr, Ytr = next_batch(5, Xtr, Ytr)
print('\n5 random samples')
print(Xtr)
print(Ytr)
And a demo run:
[0 1 2 3 4 5 6 7 8 9]
[[ 0 1 2 3 4 5 6 7 8 9]
[10 11 12 13 14 15 16 17 18 19]
[20 21 22 23 24 25 26 27 28 29]
[30 31 32 33 34 35 36 37 38 39]
[40 41 42 43 44 45 46 47 48 49]
[50 51 52 53 54 55 56 57 58 59]
[60 61 62 63 64 65 66 67 68 69]
[70 71 72 73 74 75 76 77 78 79]
[80 81 82 83 84 85 86 87 88 89]
[90 91 92 93 94 95 96 97 98 99]]
5 random samples
[9 1 5 6 7]
[[90 91 92 93 94 95 96 97 98 99]
[10 11 12 13 14 15 16 17 18 19]
[50 51 52 53 54 55 56 57 58 59]
[60 61 62 63 64 65 66 67 68 69]
[70 71 72 73 74 75 76 77 78 79]]
In order to shuffle and sampling each mini-batch, the state whether a sample has been selected inside the current epoch should also be considered. Here is an implementation which use the data in the above answer.
import numpy as np
class Dataset:
def __init__(self,data):
self._index_in_epoch = 0
self._epochs_completed = 0
self._data = data
self._num_examples = data.shape[0]
pass
@property
def data(self):
return self._data
def next_batch(self,batch_size,shuffle = True):
start = self._index_in_epoch
if start == 0 and self._epochs_completed == 0:
idx = np.arange(0, self._num_examples) # get all possible indexes
np.random.shuffle(idx) # shuffle indexe
self._data = self.data[idx] # get list of `num` random samples
# go to the next batch
if start + batch_size > self._num_examples:
self._epochs_completed += 1
rest_num_examples = self._num_examples - start
data_rest_part = self.data[start:self._num_examples]
idx0 = np.arange(0, self._num_examples) # get all possible indexes
np.random.shuffle(idx0) # shuffle indexes
self._data = self.data[idx0] # get list of `num` random samples
start = 0
self._index_in_epoch = batch_size - rest_num_examples #avoid the case where the #sample != integar times of batch_size
end = self._index_in_epoch
data_new_part = self._data[start:end]
return np.concatenate((data_rest_part, data_new_part), axis=0)
else:
self._index_in_epoch += batch_size
end = self._index_in_epoch
return self._data[start:end]
dataset = Dataset(np.arange(0, 10))
for i in range(10):
print(dataset.next_batch(5))
the output is:
[2 8 6 3 4]
[1 5 9 0 7]
[1 7 3 0 8]
[2 6 5 9 4]
[1 0 4 8 3]
[7 6 2 9 5]
[9 5 4 6 2]
[0 1 8 7 3]
[9 7 8 1 6]
[3 5 2 4 0]
the first and second (3rd and 4th,...) mini-batch correspond to one whole epoch..
I use Anaconda and Jupyter.
In Jupyter if you run ?mnist you get:
File: c:\programdata\anaconda3\lib\site-packages\tensorflow\contrib\learn\python\learn\datasets\base.py
Docstring: Datasets(train, validation, test)
In folder datesets you shall find mnist.py which contains all methods including next_batch.
The answer which is marked up above I tried the algorithm by that algorithm I am not getting results so I searched on kaggle and I saw really amazing algorithm which worked really well. Best result try this. In below algorithm **Global variable takes the input you declared above in which you read your data set.**
epochs_completed = 0
index_in_epoch = 0
num_examples = X_train.shape[0]
# for splitting out batches of data
def next_batch(batch_size):
global X_train
global y_train
global index_in_epoch
global epochs_completed
start = index_in_epoch
index_in_epoch += batch_size
# when all trainig data have been already used, it is reorder randomly
if index_in_epoch > num_examples:
# finished epoch
epochs_completed += 1
# shuffle the data
perm = np.arange(num_examples)
np.random.shuffle(perm)
X_train = X_train[perm]
y_train = y_train[perm]
# start next epoch
start = 0
index_in_epoch = batch_size
assert batch_size <= num_examples
end = index_in_epoch
return X_train[start:end], y_train[start:end]
If you would not like to get shape mismatch error in your tensorflow session run then use the below function instead of the function provided in the first solution above (https://stackoverflow.com/a/40995666/7748451) -
def next_batch(num, data, labels):
'''
Return a total of `num` random samples and labels.
'''
idx = np.arange(0 , len(data))
np.random.shuffle(idx)
idx = idx[:num]
data_shuffle = data[idx]
labels_shuffle = labels[idx]
labels_shuffle = np.asarray(labels_shuffle.values.reshape(len(labels_shuffle), 1))
return data_shuffle, labels_shuffle
Yet another implementation:
from typing import Tuple
import numpy as np
class BatchMaker(object):
def __init__(self, feat: np.array, lab: np.array) -> None:
if len(feat) != len(lab):
raise ValueError("Expected feat and lab to have the same number of samples")
self.feat = feat
self.lab = lab
self.indexes = np.arange(len(feat))
np.random.shuffle(self.indexes)
self.pos = 0
# "BatchMaker, BatchMaker, make me a batch..."
def next_batch(self, batch_size: int) -> Tuple[np.array, np.array]:
if self.pos + batch_size > len(self.feat):
np.random.shuffle(self.indexes)
self.pos = 0
batch_indexes = self.indexes[self.pos: self.pos + batch_size]
self.pos += batch_size
return self.feat[batch_indexes], self.lab[batch_indexes]
