用python绘制球体上的温度分布 [英] Plotting the temperature distribution on a sphere with python

问题描述

我有以下问题:

a在由数组x指定的球面上具有N个点，x.shape =(N，3).此数组包含其笛卡尔坐标.此外，在每个点上，我都有一个指定的温度.该数量保存在T.shape =(N，)的数组T中.

a have N points on a sphere specified by a array x, with x.shape=(N,3). This array contains their cartesian coordinates. Furthermore, at each point, I have a specified temperature. This quantity is saved in an array T, with T.shape=(N,).

是否有任何简单的方法可以使用不同的颜色将此温度分布映射到平面中?

Is there any straight forward way to map this temperature distribution into the plane using different colors?

如果它简化了任务，则位置也可以以极坐标(\ theta，\ phi)给出.

If it simplifies the task, the position can also be given in polar coordinates (\theta,\phi).

推荐答案

要绘制数据，可以使用底图.唯一的问题是contour和contourf例程都需要网格数据.这是球体上像幼稚的(和缓慢的)类似IDW的插值的示例.欢迎任何评论.

To plot your data, you can use Basemap. The only problem is, that both contour and contourf routines needs gridded data. Here is example with naive (and slow) IDW-like interpolation on sphere. Any comments are welcome.

import numpy as np
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

def cart2sph(x, y, z):
    dxy = np.sqrt(x**2 + y**2)
    r = np.sqrt(dxy**2 + z**2)
    theta = np.arctan2(y, x)
    phi = np.arctan2(z, dxy)
    theta, phi = np.rad2deg([theta, phi])
    return theta % 360, phi, r

def sph2cart(theta, phi, r=1):
    theta, phi = np.deg2rad([theta, phi])
    z = r * np.sin(phi)
    rcosphi = r * np.cos(phi)
    x = rcosphi * np.cos(theta)
    y = rcosphi * np.sin(theta)
    return x, y, z

# random data
pts = 1 - 2 * np.random.rand(500, 3)
l = np.sqrt(np.sum(pts**2, axis=1))
pts = pts / l[:, np.newaxis]
T = 150 * np.random.rand(500)

# naive IDW-like interpolation on regular grid
theta, phi, r = cart2sph(*pts.T)
nrows, ncols = (90,180)
lon, lat = np.meshgrid(np.linspace(0,360,ncols), np.linspace(-90,90,nrows))
xg,yg,zg = sph2cart(lon,lat)
Ti = np.zeros_like(lon)
for r in range(nrows):
    for c in range(ncols):
        v = np.array([xg[r,c], yg[r,c], zg[r,c]])
        angs = np.arccos(np.dot(pts, v))
        idx = np.where(angs == 0)[0]
        if idx.any():
            Ti[r,c] = T[idx[0]]
        else:
            idw = 1 / angs**2 / sum(1 / angs**2)
            Ti[r,c] = np.sum(T * idw)

# set up map projection
map = Basemap(projection='ortho', lat_0=45, lon_0=15)
# draw lat/lon grid lines every 30 degrees.
map.drawmeridians(np.arange(0, 360, 30))
map.drawparallels(np.arange(-90, 90, 30))
# compute native map projection coordinates of lat/lon grid.
x, y = map(lon, lat)
# contour data over the map.
cs = map.contourf(x, y, Ti, 15)
plt.title('Contours of T')
plt.show()

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