| Name | fast-kepler JSON |
| Version |
0.5.1
JSON |
| download |
| home_page | None |
| Summary | kepler equation solver in c for python |
| upload_time | 2024-08-24 02:10:26 |
| maintainer | None |
| docs_url | None |
| author | ReddTea |
| requires_python | >=3.6 |
| license | MIT |
| keywords |
|
| VCS |
|
| bugtrack_url |
|
| requirements |
No requirements were recorded.
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# fast_kepler
A c implementation for solving kepler's equation in c. Made for astroemperor, put in a different library for public use.
## Dependencies
This code makes use of:
- numpy
- cython
## Installation
In the console type in your work folder
```sh
pip install fast_kepler
```
## Usage
Solution to Kepler's equation. Given mean anomaly, M, and eccentricity, e,
solve for E, the eccentric anomaly, which must satisfy:
$$E - e sin(E) - M = 0$$
For a given eccentricity, and an M array, we use:
```python
import fast_kepler
M = np.sort(np.random.uniform(0, 100, size=100))
ecc = 0.11
E = fast_kepler.kepler_array(M, ecc)
```
## More on usage
We can calculate RVs:
```python
# time array of our observations
x = np.sort(np.random.uniform(0, 100, size=100))
# keplerian parameters
period = 4.1 # in days
semi_amplitude = 55 # in m/s
M0 = np.pi/3 # in rad
ecc = 0.23 # from 0 to 1
om = 3*np.pi/5 # in rad
theta = [period, semi_amplitude, M0, ecc, om]
def calc_RV(theta):
per, K, M0, ecc, om = theta
freq = 2. * np.pi / per
M = freq * x + M0
E = fast_kepler.kepler_array(M, ecc)
f = np.arctan(((1. + ecc)/(1. - ecc)) ** 0.5 * np.tan(E / 2.)) * 2.
return K * (np.cos(f + om) + ecc * np.cos(om))
# or simply:
def get_RV(theta):
per, K, M0, ecc, om = theta
return fast_kepler.calc_rv0(x, per, K, M0, ecc, om)
```
## Additional Options
You can also use a different parameterization to retrieve RVs, with time of periastron passage $T_p$ instead of the mean anomaly $M_0$:
```python
fast_kepler.calc_rv1(x, per, A, tp, ecc, w)
```
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"description": "# fast_kepler\n\nA c implementation for solving kepler's equation in c. Made for astroemperor, put in a different library for public use.\n\n## Dependencies\n\nThis code makes use of:\n - numpy\n - cython\n\n## Installation\n\nIn the console type in your work folder\n```sh\npip install fast_kepler\n```\n\n## Usage\n\nSolution to Kepler's equation. Given mean anomaly, M, and eccentricity, e,\nsolve for E, the eccentric anomaly, which must satisfy:\n\n$$E - e sin(E) - M = 0$$\n\nFor a given eccentricity, and an M array, we use:\n\n```python\nimport fast_kepler\nM = np.sort(np.random.uniform(0, 100, size=100))\necc = 0.11\nE = fast_kepler.kepler_array(M, ecc)\n```\n\n\n## More on usage\nWe can calculate RVs:\n\n```python\n# time array of our observations\nx = np.sort(np.random.uniform(0, 100, size=100))\n# keplerian parameters\nperiod = 4.1 # in days\nsemi_amplitude = 55 # in m/s\nM0 = np.pi/3 # in rad\necc = 0.23 # from 0 to 1\nom = 3*np.pi/5 # in rad\n\ntheta = [period, semi_amplitude, M0, ecc, om]\n\ndef calc_RV(theta):\n per, K, M0, ecc, om = theta\n\n freq = 2. * np.pi / per\n M = freq * x + M0\n E = fast_kepler.kepler_array(M, ecc)\n\n f = np.arctan(((1. + ecc)/(1. - ecc)) ** 0.5 * np.tan(E / 2.)) * 2.\n \n return K * (np.cos(f + om) + ecc * np.cos(om))\n\n# or simply:\n\ndef get_RV(theta):\n per, K, M0, ecc, om = theta\n return fast_kepler.calc_rv0(x, per, K, M0, ecc, om)\n```\n\n## Additional Options\n\nYou can also use a different parameterization to retrieve RVs, with time of periastron passage $T_p$ instead of the mean anomaly $M_0$:\n\n```python\nfast_kepler.calc_rv1(x, per, A, tp, ecc, w)\n```\n",
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