spherediff


Namespherediff JSON
Version 1.2.1 PyPI version JSON
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SummarySample from the diffusion kernel on any n-sphere
upload_time2023-06-05 07:32:11
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docs_urlNone
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requires_python>=3.8
license
keywords diffusion hypersphere sampling
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            # SphereDiff

## Purpose

The purpose of this package is to sample from the isotropic diffusion kernel 
on the surface of an n-dimensional unit sphere, where n is an arbitrary 
natural number dimension greater than or equal to 3.

## Installation

### From a repository checkout

```bash
pip install --user .
```

### From PyPI

```bash
pip install --user spherediff
```

## Use

The user may sample from the isotropic Gaussian distribution on the unit 
n-sphere using the `sample_spherical_kernel` function, which may be 
imported as follows:

```
>> from spherediff.sample import sample_spherical_kernel
```

This function takes three arguments and one additional, optional argument. 
The first is n, the dimension of the space in which the n-sphere is embedded. 
The second is a numpy array of shape (N, n) consisting of the n-dimensional 
unit vectors at which to center the distributions from which the samples are 
to be generated. The third is a numpy array of shape (N,) consisting of the 
scalar variance parameters of each distribution from which to generate 
samples. The fourth is a boolean flag that determines whether sampling should 
be done on the full surface of the n-sphere (if False) or on the hemisphere 
with reflecting boundary conditions for the diffusion kernel.

Example output from `sample_spherical_kernel` is:

```
>>> import numpy as np
>>> from spherediff.sample import sample_spherical_kernel
>>> np.random.seed(42)
>>> means = np.random.randn(5, 3)
>>> means /= np.linalg.norm(means, axis=1, keepdims=True)
>>> means
array([[ 0.60000205, -0.1670153 ,  0.78237039],
       [ 0.97717133, -0.15023209, -0.15022156],
       [ 0.86889694,  0.42224942, -0.25830898],
       [ 0.63675162, -0.5438697 , -0.54658314],
       [ 0.09351637, -0.73946664, -0.66666616]])
>>> vars = 0.1 * np.ones(5)
>>> sample_spherical_kernel(3, means, vars)
array([[ 0.30027556, -0.53104481,  0.79235472],
       [ 0.91657116, -0.39288942,  0.07439905],
       [ 0.81325411,  0.41495422, -0.40795926],
       [ 0.39907791, -0.44171124, -0.80350981],
       [ 0.16422958, -0.76019121, -0.62860001]])
>>> sample_spherical_kernel(3, means, vars, hemisphere=True)
array([[ 0.92723597,  0.02336567,  0.37374791],
       [ 0.99421791, -0.03878944, -0.10013055],
       [ 0.15771025,  0.6492883 , -0.74401087],
       [ 0.2418101 , -0.41127436, -0.87885225],
       [-0.11192408, -0.71437847, -0.69075061]])
```

The user may also compute the score function of the isotropic Gaussian 
distribution on the unit n-sphere, defined as the Riemannian gradient 
of the logarithm of the probability density. This may be done using the 
`score_spherical_kernel` function, which may be imported as follows:

```
from spherediff.score import score_spherical_kernel
```

This function takes four arguments and one additional, optional argument. 
The first is n, the dimension of the space in which the n-sphere is embedded. 
The second is a numpy array of shape (N, n) consisting of the n-dimensional 
unit vectors at which to evaluate the score function. The third is a numpy 
array of shape (N, n) consisting of the n-dimensional unit vectors at which 
to center the distributions of which the corresponding score functions will 
be evaluated. The fourth is a numpy array of shape (N,) consisting of the 
scalar variance parameters of each distribution. The fifth is a boolean 
flag that determines whether the distributions of interest are supported 
on the full surface of the n-sphere (if False) or on the hemisphere with 
reflecting boundary conditions for the diffusion kernel.

Example output from `score_spherical_kernel` is:

```
>>> import numpy as np
>>> from spherediff.sample import sample_spherical_kernel
>>> from spherediff.score import score_spherical_kernel
>>> np.random.seed(42)
>>> means = np.random.randn(5, 3)
>>> means /= np.linalg.norm(means, axis=1, keepdims=True)
>>> means
array([[ 0.60000205, -0.1670153 ,  0.78237039],
       [ 0.97717133, -0.15023209, -0.15022156],
       [ 0.86889694,  0.42224942, -0.25830898],
       [ 0.63675162, -0.5438697 , -0.54658314],
       [ 0.09351637, -0.73946664, -0.66666616]])
>>> vars = 0.1 * np.ones(5)
>>> x = sample_spherical_kernel(3, means, vars)
>>> x
array([[ 0.30027556, -0.53104481,  0.79235472],
       [ 0.91657116, -0.39288942,  0.07439905],
       [ 0.81325411,  0.41495422, -0.40795926],
       [ 0.39907791, -0.44171124, -0.80350981],
       [ 0.16422958, -0.76019121, -0.62860001]])
>>> score_spherical_kernel(3, x, means, vars)
array([[ 3.40175815,  3.11417869,  0.79800571],
       [ 1.12626049,  2.20918798, -2.20878198],
       [ 0.65201631,  0.12437106,  1.42627781],
       [ 2.65653386, -1.32241858,  2.04638588],
       [-0.69053884,  0.17827374, -0.39600546]])
>>> x = sample_spherical_kernel(3, means, vars, hemisphere=True)
>>> x
array([[ 0.92723597,  0.02336567,  0.37374791],
       [ 0.99421791, -0.03878944, -0.10013055],
       [ 0.15771025,  0.6492883 , -0.74401087],
       [ 0.2418101 , -0.41127436, -0.87885225],
       [-0.11192408, -0.71437847, -0.69075061]])
>>> score_spherical_kernel(3, x, means, vars, hemisphere=True)
array([[-1.74036155, -1.77246139,  4.42849462],
       [-0.0852985 , -1.00528069, -0.45751298],
       [ 2.51709283,  0.09916178,  0.62009298],
       [ 4.08775888, -1.8186883 ,  1.97580568],
       [ 1.8912707 , -0.37819329,  0.08468239]])
```

            

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    "description": "# SphereDiff\n\n## Purpose\n\nThe purpose of this package is to sample from the isotropic diffusion kernel \non the surface of an n-dimensional unit sphere, where n is an arbitrary \nnatural number dimension greater than or equal to 3.\n\n## Installation\n\n### From a repository checkout\n\n```bash\npip install --user .\n```\n\n### From PyPI\n\n```bash\npip install --user spherediff\n```\n\n## Use\n\nThe user may sample from the isotropic Gaussian distribution on the unit \nn-sphere using the `sample_spherical_kernel` function, which may be \nimported as follows:\n\n```\n>> from spherediff.sample import sample_spherical_kernel\n```\n\nThis function takes three arguments and one additional, optional argument. \nThe first is n, the dimension of the space in which the n-sphere is embedded. \nThe second is a numpy array of shape (N, n) consisting of the n-dimensional \nunit vectors at which to center the distributions from which the samples are \nto be generated. The third is a numpy array of shape (N,) consisting of the \nscalar variance parameters of each distribution from which to generate \nsamples. The fourth is a boolean flag that determines whether sampling should \nbe done on the full surface of the n-sphere (if False) or on the hemisphere \nwith reflecting boundary conditions for the diffusion kernel.\n\nExample output from `sample_spherical_kernel` is:\n\n```\n>>> import numpy as np\n>>> from spherediff.sample import sample_spherical_kernel\n>>> np.random.seed(42)\n>>> means = np.random.randn(5, 3)\n>>> means /= np.linalg.norm(means, axis=1, keepdims=True)\n>>> means\narray([[ 0.60000205, -0.1670153 ,  0.78237039],\n       [ 0.97717133, -0.15023209, -0.15022156],\n       [ 0.86889694,  0.42224942, -0.25830898],\n       [ 0.63675162, -0.5438697 , -0.54658314],\n       [ 0.09351637, -0.73946664, -0.66666616]])\n>>> vars = 0.1 * np.ones(5)\n>>> sample_spherical_kernel(3, means, vars)\narray([[ 0.30027556, -0.53104481,  0.79235472],\n       [ 0.91657116, -0.39288942,  0.07439905],\n       [ 0.81325411,  0.41495422, -0.40795926],\n       [ 0.39907791, -0.44171124, -0.80350981],\n       [ 0.16422958, -0.76019121, -0.62860001]])\n>>> sample_spherical_kernel(3, means, vars, hemisphere=True)\narray([[ 0.92723597,  0.02336567,  0.37374791],\n       [ 0.99421791, -0.03878944, -0.10013055],\n       [ 0.15771025,  0.6492883 , -0.74401087],\n       [ 0.2418101 , -0.41127436, -0.87885225],\n       [-0.11192408, -0.71437847, -0.69075061]])\n```\n\nThe user may also compute the score function of the isotropic Gaussian \ndistribution on the unit n-sphere, defined as the Riemannian gradient \nof the logarithm of the probability density. This may be done using the \n`score_spherical_kernel` function, which may be imported as follows:\n\n```\nfrom spherediff.score import score_spherical_kernel\n```\n\nThis function takes four arguments and one additional, optional argument. \nThe first is n, the dimension of the space in which the n-sphere is embedded. \nThe second is a numpy array of shape (N, n) consisting of the n-dimensional \nunit vectors at which to evaluate the score function. The third is a numpy \narray of shape (N, n) consisting of the n-dimensional unit vectors at which \nto center the distributions of which the corresponding score functions will \nbe evaluated. The fourth is a numpy array of shape (N,) consisting of the \nscalar variance parameters of each distribution. The fifth is a boolean \nflag that determines whether the distributions of interest are supported \non the full surface of the n-sphere (if False) or on the hemisphere with \nreflecting boundary conditions for the diffusion kernel.\n\nExample output from `score_spherical_kernel` is:\n\n```\n>>> import numpy as np\n>>> from spherediff.sample import sample_spherical_kernel\n>>> from spherediff.score import score_spherical_kernel\n>>> np.random.seed(42)\n>>> means = np.random.randn(5, 3)\n>>> means /= np.linalg.norm(means, axis=1, keepdims=True)\n>>> means\narray([[ 0.60000205, -0.1670153 ,  0.78237039],\n       [ 0.97717133, -0.15023209, -0.15022156],\n       [ 0.86889694,  0.42224942, -0.25830898],\n       [ 0.63675162, -0.5438697 , -0.54658314],\n       [ 0.09351637, -0.73946664, -0.66666616]])\n>>> vars = 0.1 * np.ones(5)\n>>> x = sample_spherical_kernel(3, means, vars)\n>>> x\narray([[ 0.30027556, -0.53104481,  0.79235472],\n       [ 0.91657116, -0.39288942,  0.07439905],\n       [ 0.81325411,  0.41495422, -0.40795926],\n       [ 0.39907791, -0.44171124, -0.80350981],\n       [ 0.16422958, -0.76019121, -0.62860001]])\n>>> score_spherical_kernel(3, x, means, vars)\narray([[ 3.40175815,  3.11417869,  0.79800571],\n       [ 1.12626049,  2.20918798, -2.20878198],\n       [ 0.65201631,  0.12437106,  1.42627781],\n       [ 2.65653386, -1.32241858,  2.04638588],\n       [-0.69053884,  0.17827374, -0.39600546]])\n>>> x = sample_spherical_kernel(3, means, vars, hemisphere=True)\n>>> x\narray([[ 0.92723597,  0.02336567,  0.37374791],\n       [ 0.99421791, -0.03878944, -0.10013055],\n       [ 0.15771025,  0.6492883 , -0.74401087],\n       [ 0.2418101 , -0.41127436, -0.87885225],\n       [-0.11192408, -0.71437847, -0.69075061]])\n>>> score_spherical_kernel(3, x, means, vars, hemisphere=True)\narray([[-1.74036155, -1.77246139,  4.42849462],\n       [-0.0852985 , -1.00528069, -0.45751298],\n       [ 2.51709283,  0.09916178,  0.62009298],\n       [ 4.08775888, -1.8186883 ,  1.97580568],\n       [ 1.8912707 , -0.37819329,  0.08468239]])\n```\n",
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