What is the equivalent of np.std() in TensorFlow?
Question:
Just looking for the equivalent of np.std() in TensorFlow to calculate the standard deviation of a tensor.
Answers:
To get the mean and variance just use tf.nn.moments
.
mean, var = tf.nn.moments(x, axes=[1])
For more on tf.nn.moments
params see docs
You can also use reduce_std
in the following code adapted from Keras:
#coding=utf-8
import numpy as np
import tensorflow as tf
def reduce_var(x, axis=None, keepdims=False):
"""Variance of a tensor, alongside the specified axis.
# Arguments
x: A tensor or variable.
axis: An integer, the axis to compute the variance.
keepdims: A boolean, whether to keep the dimensions or not.
If `keepdims` is `False`, the rank of the tensor is reduced
by 1. If `keepdims` is `True`,
the reduced dimension is retained with length 1.
# Returns
A tensor with the variance of elements of `x`.
"""
m = tf.reduce_mean(x, axis=axis, keep_dims=True)
devs_squared = tf.square(x - m)
return tf.reduce_mean(devs_squared, axis=axis, keep_dims=keepdims)
def reduce_std(x, axis=None, keepdims=False):
"""Standard deviation of a tensor, alongside the specified axis.
# Arguments
x: A tensor or variable.
axis: An integer, the axis to compute the standard deviation.
keepdims: A boolean, whether to keep the dimensions or not.
If `keepdims` is `False`, the rank of the tensor is reduced
by 1. If `keepdims` is `True`,
the reduced dimension is retained with length 1.
# Returns
A tensor with the standard deviation of elements of `x`.
"""
return tf.sqrt(reduce_var(x, axis=axis, keepdims=keepdims))
if __name__ == '__main__':
x_np = np.arange(10).reshape(2, 5).astype(np.float32)
x_tf = tf.constant(x_np)
with tf.Session() as sess:
print(sess.run(reduce_std(x_tf, keepdims=True)))
print(sess.run(reduce_std(x_tf, axis=0, keepdims=True)))
print(sess.run(reduce_std(x_tf, axis=1, keepdims=True)))
print(np.std(x_np, keepdims=True))
print(np.std(x_np, axis=0, keepdims=True))
print(np.std(x_np, axis=1, keepdims=True))
You can also use directly:
tf.math.reduce_std(
input_tensor, axis=None, keepdims=False, name=None
)
Just looking for the equivalent of np.std() in TensorFlow to calculate the standard deviation of a tensor.
To get the mean and variance just use tf.nn.moments
.
mean, var = tf.nn.moments(x, axes=[1])
For more on tf.nn.moments
params see docs
You can also use reduce_std
in the following code adapted from Keras:
#coding=utf-8
import numpy as np
import tensorflow as tf
def reduce_var(x, axis=None, keepdims=False):
"""Variance of a tensor, alongside the specified axis.
# Arguments
x: A tensor or variable.
axis: An integer, the axis to compute the variance.
keepdims: A boolean, whether to keep the dimensions or not.
If `keepdims` is `False`, the rank of the tensor is reduced
by 1. If `keepdims` is `True`,
the reduced dimension is retained with length 1.
# Returns
A tensor with the variance of elements of `x`.
"""
m = tf.reduce_mean(x, axis=axis, keep_dims=True)
devs_squared = tf.square(x - m)
return tf.reduce_mean(devs_squared, axis=axis, keep_dims=keepdims)
def reduce_std(x, axis=None, keepdims=False):
"""Standard deviation of a tensor, alongside the specified axis.
# Arguments
x: A tensor or variable.
axis: An integer, the axis to compute the standard deviation.
keepdims: A boolean, whether to keep the dimensions or not.
If `keepdims` is `False`, the rank of the tensor is reduced
by 1. If `keepdims` is `True`,
the reduced dimension is retained with length 1.
# Returns
A tensor with the standard deviation of elements of `x`.
"""
return tf.sqrt(reduce_var(x, axis=axis, keepdims=keepdims))
if __name__ == '__main__':
x_np = np.arange(10).reshape(2, 5).astype(np.float32)
x_tf = tf.constant(x_np)
with tf.Session() as sess:
print(sess.run(reduce_std(x_tf, keepdims=True)))
print(sess.run(reduce_std(x_tf, axis=0, keepdims=True)))
print(sess.run(reduce_std(x_tf, axis=1, keepdims=True)))
print(np.std(x_np, keepdims=True))
print(np.std(x_np, axis=0, keepdims=True))
print(np.std(x_np, axis=1, keepdims=True))
You can also use directly:
tf.math.reduce_std(
input_tensor, axis=None, keepdims=False, name=None
)