I have array of shape (3,5,96,96), where channels= 3, number of frames = 5 and height and width = 96
I want to iterate over dimension 5 to get images with size (3,96,96). The code which I have tried is below.
b = frame.shape[1]
for i in range(b):
fr = frame[:,i,:,:]
But this is not working.
You could swap axis (using numpy.swapaxes(a, axis1, axis2) to get the second (frame) in first position
import numpy as np
m = np.zeros((3, 5, 96, 96))
n = np.swapaxes(m, 0, 1)
print(n.shape)
(5, 3, 96, 96)
You need to iterate over the first axis to achieve your desired result, this means you need to move the axis you want to iterate over to the first position. You can achieve this with np.moveaxis
m = np.zeros((3, 5, 96, 96))
np.moveaxis(m, 1, 0).shape
(5, 3, 96, 96)
Related
First things first: I'm relatively new to TensorFlow.
I'm trying to implement a custom layer in tensorflow.keras and I'm having relatively hard time when I try to achieve the following:
I've got 3 Tensors (x,y,z) of shape (?,49,3,3,32) [where ? is the batch size]
On each Tensor I compute the sum over the 3rd and 4th axes [thus I end up with 3 Tensors of shape (?,49,32)]
By doing an argmax (A)on the above 3 Tensors (?,49,32) I get a single (?,49,32) Tensor
Now I want to use this tensor to select slices from the initial x,y,z Tensors in the following form:
Each element in the last dimension of A corresponds to the selected Tensor.
(aka: 0 = X, 1 = Y, 2 = Z)
The index of the last dimension of A corresponds to the slice that I would like to extract from the Tensor last dimension.
I've tried to achieve the above using tf.gather but I had no luck. Then I tried using a series of tf.map_fn, which is ugly and computationally costly.
To simplify the above:
let's say we've got an A array of shape (3,3,3,32). Then the numpy equivalent of what I try to achieve is this:
import numpy as np
x = np.random.rand(3,3,32)
y = np.random.rand(3,3,32)
z = np.random.rand(3,3,32)
x_sums = np.sum(np.sum(x,axis=0),0);
y_sums = np.sum(np.sum(y,axis=0),0);
z_sums = np.sum(np.sum(z,axis=0),0);
max_sums = np.argmax([x_sums,y_sums,z_sums],0)
A = np.array([x,y,z])
tmp = []
for i in range(0,len(max_sums)):
tmp.append(A[max_sums[i],:,:,i)
output = np.transpose(np.stack(tmp))
Any suggestions?
ps: I tried tf.gather_nd but I had no luck
This is how you can do something like that with tf.gather_nd:
import tensorflow as tf
# Make example data
tf.random.set_seed(0)
b = 10 # Batch size
x = tf.random.uniform((b, 49, 3, 3, 32))
y = tf.random.uniform((b, 49, 3, 3, 32))
z = tf.random.uniform((b, 49, 3, 3, 32))
# Stack tensors together
data = tf.stack([x, y, z], axis=2)
# Put reduction axes last
data_t = tf.transpose(data, (0, 1, 5, 2, 3, 4))
# Reduce
s = tf.reduce_sum(data_t, axis=(4, 5))
# Find largest sums
idx = tf.argmax(s, 3)
# Make gather indices
data_shape = tf.shape(data_t, idx.dtype)
bb, ii, jj = tf.meshgrid(*(tf.range(data_shape[i]) for i in range(3)), indexing='ij')
# Gather result
output_t = tf.gather_nd(data_t, tf.stack([bb, ii, jj, idx], axis=-1))
# Reorder axes
output = tf.transpose(output_t, (0, 1, 3, 4, 2))
print(output.shape)
# TensorShape([10, 49, 3, 3, 32])
I have a dataset where one of the similar looking class is imbalanced. It is a number dataset where class labels go from 1 to 10.
Grouping by label (y) on the training set gives the following output:
(array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], dtype=uint8), array([13861, 10585, 8497, 7458, 6882, 5727, 5595, 5045, 4659,
4948]))
As could be seen 1 has 13861 data-points and 7 has only 5595 data-points.
To avoid the class imbalance between 1 and 7 I want to put some extra images for 7 class.
Here is train set:
from scipy.io import loadmat
train = loadmat('train.mat')
extra = loadmat('extra.mat')
Both train and extra are dictionaries with 2 keys X and y each.
Here is the shape of train and extra:
train['X'] --> (32, 32, 3, 73257)
# 73257 images of 32x32x3
train['y'] --> (73257,1)
# 73257 labels of corresponding images
extra['X'] --> (32, 32, 3, 531131)
# 531131 images of 32x32x3
extra['y'] --> (531131, 1)
# 531131 labels of corresponding images
Now, I want to update train dataset with labels from extra, primarily taking x% of data with label 7 in extra into train. How could I do this?
I tried the following:
arr, _ = np.where(extra['y'] == 7)
c = np.concatenate(X_train, extra['X'][arr])
But I get an error saying IndexError: index 32 is out of bounds for axis 0 with size 32
Here is a working example on just numpy arrays that easily translates to your case. As you have edited, use numpy.where to find the labels you want on extra['y'] and keep these indices. These are then used together with numpy.append to concatenate (last axis for X and first axis for y) your original dataset with the extra one.
import numpy as np
np.random.seed(100)
# First find the indices of your y_extra with label 7
x_extra = np.random.rand(32, 32, 3, 10)
y_extra = np.random.randint(0, 9, size=(10,1))
indices = np.where(y_extra==7)[0] # indices [3,4] are 7 with seed=100
# Now use this indices to concatenate them in the original datase
np.random.seed(101)
x_original = np.random.rand(32, 32, 3, 10)
y_original = np.random.randint(1, 10, size=(10,1))
print(x_original.shape, x_extra[..., indices].shape) # (32, 32, 3, 10) (32, 32, 3, 2)
print(y_original.shape, y_extra[indices].shape) # (10, 1) (2, 1)
x_final = np.append(x_original, x_extra[..., indices], axis=-1)
y_final = np.append(y_original, y_extra[indices], axis=0)
print(x_final.shape, y_final.shape) # (32, 32, 3, 12) (12, 1)
I have a numpy array of size image_stack 64x28x28x3 which correspond to 64 images of size 28x28x3. What I want is to construct an image of size 224x224x3 which will contain all my images that are in the initial array. How can I do so in numpy? So far I have the code for stacking the images in the same line, however I want 8 lines of 8 columns instead. My code so far:
def tile_images(image_stack):
"""Given a stacked tensor of images, reshapes them into a horizontal tiling for display."""
assert len(image_stack.shape) == 4
image_list = [image_stack[i, :, :, :] for i in range(image_stack.shape[0])]
tiled_images = np.concatenate(image_list, axis=1)
return tiled_images
Does the following reshape, transpose, reshape trick work?
x.shape # (64, 28, 28, 3)
mosaic = x.reshape(8, 8, 28, 28, 3).transpose((0, 2, 1, 3, 4)).reshape(224, 224, 3)
The first reshape breaks your 64 into lines and columns. Transpose rearranges their order so that we can collapse them in a meaningful way.
Your function would then look like:
def tile_images(x):
dims = x.shape
assert len(dims) == 4
stack_dim = int(np.sqrt(dims[0]))
res = x.reshape(stack_dim, stack_dim, *dims[1:]).transpose((0, 2, 1, 3, 4))
tile_size = res.shape[0] * res.shape[1]
return res.reshape(tile_size, tile_size, -1)
This is my first nontrivial use of numpy, and I'm having some trouble in one spot.
So, I have colors, a (xsize + 2, ysize + 2, 3) ndarray, and newlife, a (xsize + 2, ysize + 2) ndarray of booleans. I want to add a random value between -5 and 5 to all three values in colors at all positions where newlife is true. In other words newlife maps 2D vectors to whether or not I want to add a random value to the color in colors at that position.
I've tried a million variations on this:
colors[np.nonzero(newlife)] += (np.random.random_sample((xsize + 2,ysize + 2, 3)) * 10 - 5)
but I keep getting stuff like
ValueError: operands could not be broadcast together with shapes (589,3) (130,42,3) (589,3)
How do I do this?
I think this does what you want:
# example data
colors = np.random.randint(0, 100, (5,4,3))
newlife = np.random.randint(0, 2, (5,4), bool)
# create values to add, then mask with newlife
to_add = np.random.randint(-5,6, (5,4,3))
to_add[~newlife] = 0
# modify in place
colors += to_add
This changes the colors in-place assuming uint8 dtype. Both assumptions are not essential:
import numpy as np
n_x, n_y = 2, 2
colors = np.random.randint(5, 251, (n_x+2, n_y+2, 3), dtype=np.uint8)
mask = np.random.randint(0, 2, (n_x+2, n_y+2), dtype=bool)
n_change = np.count_nonzero(mask)
print(colors)
print(mask)
colors[mask] += np.random.randint(-5, 6, (n_change, 3), dtype=np.int8).view(np.uint8)
print(colors)
The easiest way of understanding this is to look at the shape of colors[mask].
So I have 2 images, X and Y, as numpy arrays, each of shape (3, 30, 30): that is, 3 channels (RGB), each of height and width 30 pixels. I'd like to pair them up into a numpy array to get a specific output shape:
my_pair = pair_up_images(X, Y)
my_pair.shape = (2, 3, 30, 30)
Such that I can get the original images by slicing:
my_pair[0] == X
my_pair[1] == Y
After a few attempts, I keep getting either:
my_pair.shape = (2,) #By converting the images into lists and adding them.
This works as well, but the next step in the pipeline just requires a shape (2, 3, 30, 30)
my_pair.shape = (6, 30, 30) # using np.vstack
my_pair.shape = (3, 60, 30) # using np.hstack
Thanks!
Simply:
Z = np.array([X, Y])
Z.shape
Out[62]: (2, 3, 30, 30)