怎么用python画指北针？
先放图
然后下面的python代码
from matplotlib.patches import *
def get_circle(x1, y1, x2, y2, x3, y3):
"""
根据三个点，返回外接圆的中心和半径
:param x1:
:param y1:
:param x2:
:param y2:
:param x3:
:param y3:
:return: x,y,r
"""
a = x1 - x2
b = y1 - y2
c = x1 - x3
d = y1 - y3
a1 = ((x1 * x1 - x2 * x2) + (y1 * y1 - y2 * y2)) / 2.0
a2 = ((x1 * x1 - x3 * x3) + (y1 * y1 - y3 * y3)) / 2.0
theta = b * c - a * d
if abs(theta) < 1e-7:
raise ValueError("compute circle error!")
x0 = (b * a2 - d * a1) / theta
y0 = (c * a1 - a * a2) / theta
r = np.sqrt(pow((x1 - x0), 2) + pow((y1 - y0), 2))
return x0, y0, r
def add_north(ax, x, y, text_size=15, arrow_width=0.05,
text_pad=0.01, arrow_height=None,
line_width=1, add_circle=True):
"""
给子图添加一个指北针，这里的长度，间隔等是0-1之间的小数
:param ax: 子图句柄
:param x: 指针尖的x坐标[0-1]
:param y: 指针尖的y坐标[0-1]
:param text_size: N字符大小
:param arrow_width: 箭头的宽度
:param text_pad: 文字和箭头的间隔
:param arrow_height: 箭头的宽度
:param line_width: 线条的宽度
:param add_circle: 是否添加圆
:return: None
"""
if arrow_height is None:
arrow_height = arrow_width * 1.87
x_min, x_max = ax.get_xlim()
y_min, y_max = ax.get_ylim()
width = x_max - x_min
height = y_max - y_min
left = (x_min + width * (x - arrow_width * 0.5), y_min + height * (y - arrow_height))
right = (x_min + width * (x + arrow_width * 0.5), left[1])
top = (x_min + width * x, y_min + height * y)
bottom_center = (top[0], left[1] + 0.27 * (top[1] - left[1]))
left_patch = Polygon([left, top, bottom_center], color='k',
linewidth=line_width)
right_patch = Polygon([bottom_center, top, right],
facecolor='none',
edgecolor='k', linewidth=line_width)
ax.add_patch(left_patch)
ax.add_patch(right_patch)
if add_circle:
circle_x, circle_y, r = get_circle(*top, *left, *right)
circle_patch = Circle((circle_x, circle_y), r,
facecolor='none',
edgecolor='k',
linewidth=line_width)
ax.add_patch(circle_patch)
ax.text(s='N',
x=top[0],
y=top[1] + text_pad * height,
fontsize=text_size,
horizontalalignment='center',
verticalalignment='bottom')
按照函数签名使用即可