How to create a Rotation Matrix in Tensorflow

Question

I want to create a rotation matrix in tensorflow where all parts of it are tensors.

What I have:

def rotate(tf, points, theta):
    rotation_matrix = [[tf.cos(theta), -tf.sin(theta)],
                       [tf.sin(theta), tf.cos(theta)]]
    return tf.matmul(points, rotation_matrix)

But this says that rotation_matrix is a list of tensors instead of a tensor itself. theta is also a tensor object that is passed in at run time.

Answer 1

An Option I found that works is to use pack but if there is a better way please post an answer:

def rotate(tf, points, theta):
    top = tf.pack([tf.cos(theta), -tf.sin(theta)])
    bottom = tf.pack([tf.sin(theta), tf.cos(theta)])
    rotation_matrix = tf.pack([top, bottom])
    return tf.matmul(points, rotation_matrix)

Answer 2

with two operations:

def rotate(tf, points, theta):
    rotation_matrix = tf.pack([tf.cos(theta),
                              -tf.sin(theta),  
                               tf.sin(theta),
                               tf.cos(theta)])
    rotation_matrix = tf.reshape(rotation_matrix, (2,2))
    return tf.matmul(points, rotation_matrix)