Implemented the calculation of Associated Legendre polynomials using scipy, eliminating the dependency on the pyshtools package.

README.md

@@ -123,24 +123,26 @@ pip install pyatmos --upgrade # to upgrade a pre-existing installation
 ```
 
 ## Change log
+- **1.2.6 — Mar 08, 2024**
+  - Implemented the calculation of Associated Legendre polynomials using `scipy`, eliminating the dependency on the `pyshtools` package.
 - **1.2.5 — Jul 16, 2023**
-  - Added time system for loading/updating the EOP file and Leap Second file from IERS
+  - Added time system for loading/updating the EOP file and Leap Second file from IERS.
 - **1.2.4 — Feb 16, 2023**
-  - Changed functions `read_sw_nrlmsise00` and `get_sw` due to the space weather file changed from 'SW-ALL.txt' to 'SW-ALL.csv'
+  - Changed functions `read_sw_nrlmsise00` and `get_sw` due to the space weather file changed from 'SW-ALL.txt' to 'SW-ALL.csv'.
   - Deleted the colored-progress bar for downloading space weather file, and use `wget` instead.
 - **1.2.3 — Jun 7, 2021**
   - Added atmospheric models **JB2008**
-  - Changed the output of the result to an instance
+  - Changed the output of the result to an instance.
-  - Improved the code structure for NRLMSISE-00, and the running speed is nearly threefold
+  - Improved the code structure for NRLMSISE-00, and the running speed is nearly threefold.
 - **1.2.1 — Jan 22, 2021**
-  - Added **Exponential Atmosphere** up to 1000 km
+  - Added **Exponential Atmosphere** up to 1000 km.
-  - Added **Committee on Extension to the Standard Atmosphere(COESA)** up to 1000 km
+  - Added **Committee on Extension to the Standard Atmosphere(COESA)** up to 1000 km.
-  - Completed part of the help documentation for NRLMSISE-00
+  - Completed part of the help documentation for NRLMSISE-00.
-  - Improved the code structure to make it easier to read
+  - Improved the code structure to make it easier to read.
 - **1.1.2 — Jul 26, 2020**
-  - Added colored-progress bar for downloading data
+  - Added colored-progress bar for downloading data.
 - **1.1.0 — Mar 29,  2020**
-  - Added the International Standard Atmosphere(ISA) Model up to 86kms  
+  - Added the International Standard Atmosphere(ISA) Model.  
 
 ## Next release
 

pyatmos/msise/nrlmsise00_subfunc.py

@@ -1,6 +1,6 @@
 import numpy as np
 from scipy.interpolate import CubicSpline
-from pyshtools.legendre import PLegendreA,PlmIndex
+from scipy.special import lpmv
 import pkg_resources
 
 def nrlmsis00_data():
@@ -275,9 +275,30 @@ def sg0(ex,p,ap):
                 g0(ap[6],p)*ex**12)*(1-ex**8)/(1-ex))/sumex(ex)
 
 # =============== 3hr magnetic activity functions =================== #
+def PLegendreA(lmax, x):
+    """
+    Calculates all unnormalized associated Legendre polynomials up to degree lmax for a given x value.
+
+    Inputs:
+        lmax -> [int] The maximum degree of the polynomials to compute.
+        x -> [float] The value at which to evaluate the polynomials.
+    Outputs:
+        res -> [array-like] An array of shape (lmax + 1) * (lmax + 2) // 2 containing the values of the unnormalized associated Legendre polynomials P_l^m(x) for l = 0, 1, ..., lmax and m = 0, 1, ..., l.
+    Note: The Condon-Shortley phase is excluded.    
+    """
+    res = np.zeros((lmax + 1) * (lmax + 2) // 2)
+
+    # Compute P_l^m(x) for all l and m
+    k = 0
+    for l in range(lmax + 1):
+        for m in range(l + 1):
+            res_k = lpmv(m, l, x)
+            if m%2: res_k *= -1
+            res[k] = res_k
+            k += 1
+    return res
 
 def lengendre(g_lat,lmax = 8):
-    # Index of PLegendreA_x can be calculated by PlmIndex(l,m)
     x = np.sin(np.deg2rad(g_lat))
     PLegendreA_x = PLegendreA(lmax,x)
     return PLegendreA_x

setup.py

@@ -2,7 +2,7 @@ from setuptools import setup,find_packages
 
 setup(
     name = 'pyatmos',
-    version = '1.2.5',
+    version = '1.2.6',
     description = 'A package to estimate the vertical structure of atmosphere with various atmospheric density models',
     author = 'Chunxiao Li',
     author_email = 'lcx366@126.com',
@@ -11,13 +11,14 @@ setup(
     long_description_content_type = 'text/markdown',
     long_description = open('README.md', 'rb').read().decode('utf-8'),
     keywords = ['coesa76','nrlmsise00','jb2008'],
-    python_requires = '>=3.8',
+    python_requires = '>=3.10',
     classifiers = [
         'Development Status :: 4 - Beta',
         'Intended Audience :: Education',
         'Intended Audience :: Science/Research',
-        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
+        'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12',
         'License :: OSI Approved :: MIT License',
         ],
     packages = find_packages(),
@@ -29,7 +30,6 @@ setup(
         'numba',
         'pandas',
         'astropy',
-        'pyshtools',
         'wget'
         ]
     )