等值线图的Python绘制方法
等值线图或等高线图在科学界经常用到，它是由一些封闭的曲线组成的，来表示三维结构表面。
虽然看起来复杂，其实用matplotlib实现起来并不难。
代码如下：
import numpy as np
import matplotlib.pyplot as plt
dx=0.01;dy=0.01
x=np.arange(-2.0,2.0,dx)
y=np.arange(-2.0,2.0,dy)
X,Y=np.meshgrid(x,y)
def f(x,y):
return(1-y**5+x**5)*np.exp(-x**2-y**2)
C=plt.contour(X,Y,f(X,Y),8,colors='black') #生成等值线图
plt.contourf(X,Y,f(X,Y),8)
plt.clable(C,inline=1,fontsize=10)
结果如下：
使用等值线图，在图的一侧增加图例作为图表中所用颜色的说明几乎是必需的，在上述代码最后增加colorbar()函数就可以实现。
plt.colorbar()
python等值线图绘制,计算合适的等值线间距
python按照给定坐标点进行插值并绘制等值线图
import matplotlib.pyplot as plt
import numpy as np
import math
import pandas as pd
import io
import copy
def get_gap(gap):
gap = str(gap)
gap_len = len(gap)
gap_list = list(map(int, gap))
top_value = int(gap_list[0])
gap_bottom = top_value * (10 ** (gap_len - 1))
gap_mid = gap_bottom + int((10 ** (gap_len - 1) / 2))
gap_top = (top_value + 1) * (10 ** (gap_len - 1))
gap_value = [gap_bottom, gap_mid, gap_top]
gap_bottom_dis = abs(int(gap) - gap_bottom)
gap_mid_dis = abs(int(gap) - gap_mid)
gap_top_dis = abs(int(gap) - gap_top)
range_list = [gap_bottom_dis, gap_mid_dis, gap_top_dis]
min_i = 0
for i in range(len(range_list)):
if range_list[i] < range_list[min_i]:
min_i = i
final_gap = gap_value[min_i]
return int(final_gap)
def interpolation(lon, lat, lst):
# 网格插值——反距离权重法
p0 = [lon, lat]
sum0 = 0
sum1 = 0
temp = []
for point in lst:
if lon == point[0] and lat == point[1]:
return point[2]
Di = distance(p0, point)
ptn = copy.deepcopy(point)
ptn = list(ptn)
ptn.append(Di)
temp.append(ptn)
temp1 = sorted(temp, key=lambda point: point[3])
for point in temp1[0:15]:
sum0 += point[2] / math.pow(point[3], 2)
sum1 += 1 / math.pow(point[3], 2)
return sum0 / sum1
def distance(p, pi):
dis = (p[0] - pi[0]) * (p[0] - pi[0]) + (p[1] - pi[1]) * (p[1] - pi[1])
m_result = math.sqrt(dis)
return m_result
def gap_equal_line_value(min_value, max_value , n_group):
# 计算较为合适的gap来获取最终的分界值
n_group = int(n_group)
gap = abs((max_value - min_value) / n_group)
if gap >= 1:
gap = int(math.ceil(gap))
final_gap = get_gap(gap)
else:
gap_effect = np.float('%.{}g'.format(1) % Decimal(gap))
gap_effect = gap * (10 ** (len(str(gap_effect)) - 2))
gap_multi = gap_effect / gap
gap = math.ceil(gap_effect)
final_gap = get_gap(gap)
final_gap = final_gap / gap_multi
#final_gap = np.float('%.{}g'.format(4) % Decimal(final_gap))
bottom = min_value + final_gap
if final_gap < 1:
final_bottom = bottom
else:
if abs(bottom) >= 1:
bottom_effect = math.ceil(abs(bottom))
final_bottom = get_gap(bottom_effect)
else:
bottom_effect = np.float('%.{}g'.format(1) % (abs(bottom)))
bottom_multi = bottom_effect / (abs(bottom))
bottom_effect = math.ceil(bottom_effect)
final_bottom = get_gap(bottom_effect)
final_bottom = (final_bottom / bottom_multi)
if bottom < 0:
final_bottom = final_bottom * (-1)
else:
pass
# print(final_bottom)
#final_bottom = keep_decimal(final_bottom)
equal_line_value = []
if math.floor(min_value) >= final_bottom:
equal_line_value.append(final_bottom-1)
else:
equal_line_value.append(math.floor(min_value))
equal_line_value.append(final_bottom)
for i in range(1, n_group-1):
final_bottom = final_bottom + final_gap
equal_line_value.append(final_bottom)
final_bottom = final_bottom + final_gap
if final_bottom <= max_value:
equal_line_value.append(math.ceil(max_value))
else:
equal_line_value.append(final_bottom)
print(equal_line_value)
return equal_line_value
def equal_line_value(min_value, max_value, n_group):
# 直接按照分组字数计算分界值
n_group = int(n_group)
gap = abs((max_value - min_value) / n_group)
equal_line_value = []
if gap <= 0:
gap_flag = False #gap为0
equal_line_value.append(max_value-1)
equal_line_value.append(max_value+1)
else:
gap_flag = True
equal_line_value.append(min_value)
now_value = min_value
for i in range(1, n_group):
now_value = now_value + gap
equal_line_value.append(now_value)
equal_line_value.append(max_value)
res = {
'gap_flag': gap_flag,
'equal_line_value': equal_line_value
}
return res
def contour_line_plot(grid_x_plot, grid_y_plot, f_plot, levels,x_long,y_long,n_group):
n_group = int(n_group)
color1 = '#74E3AD'
color2 = '#17BD6D'
color3 = '#05A156'
color4 = '#038A49'
color5 = '#165C3A'
color6 = '#BDBDBD'
color7= '#848484'
color8 = '#FA58F4'
color9 = '#FF00BF'
color10 = '#FF0080'
color11 = '#8A084B'
color12 = '#3B0B24'
Colors_all = (color1, color2, color3, color4, color5, color6, color7, color8, color9, color10, color11, color12)
Colors = Colors_all[0:n_group]
fig = plt.figure(figsize=(x_long,y_long))
ax = plt.subplot()
ax.contourf(grid_x_plot, grid_y_plot, f_plot, levels=levels, colors = Colors)
ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)
ax.spines['bottom'].set_visible(False)
ax.spines['left'].set_visible(False)
ax.set_xticks([])
ax.set_yticks([])
plt.subplots_adjust(top=1, bottom=0, right=1, left=0, hspace=0, wspace=0)
plt.margins(0, 0)
# 输出为二进制流
canvas = fig.canvas
buffer = io.BytesIO() # 获取输入输出流对象
canvas.print_png(buffer) # 将画布上的内容打印到输入输出流对象
data = buffer.getvalue() # 获取流的值
buffer.close()
plt.close()
# with open('hhh.png', mode='wb') as f:
# f.write(data)
return data
def contour_line(data,n_group):
'''
data:数组，[[x1,y1,value1],[x2,y2,value2],[x2,y2,value2],......]
例：data = [[5,5,11],[5,25,21],[10,25,45],[10,5,5],[8,5,60]]
n_group:分组组数
'''
data = pd.DataFrame(data,columns=['x', 'y', 'f'])
min_x = data['x'].min()
max_x = data['x'].max()
min_y = data['y'].min()
max_y = data['y'].max()
# 设置等值线图大小
x_long = 40.0
y_long = 40.0
lst = data.iloc[:, 0:3].values
# 设置网格大小
n_grid = 50
grid_x = np.linspace(min_x, max_x, n_grid)
grid_y = np.linspace(min_y, max_y, n_grid)
# 得到所有网格坐标点
data_xy_list = []
for i in range(len(grid_x)):
for j in range(len(grid_y)):
data_xy_list.append([grid_x[i], grid_y[j]])
data_xy = pd.DataFrame(data_xy_list, columns=['x', 'y'])
# 得到所有网格坐标点和对应的值
insert_value_list = []
for i in range(len(data_xy)):
value = interpolation(data_xy.iloc[i, 0], data_xy.iloc[i, 1], lst)
insert_value_list.append([data_xy.iloc[i, 0], data_xy.iloc[i, 1], value])
insert_data = pd.DataFrame(insert_value_list, columns=['x', 'y', 'f'])
# 得到等值线的分界值
equal_value_res = equal_line_value(insert_data.loc[:, ['f']].min()[0], insert_data.loc[:, ['f']].max()[0],n_group)
equal_value_list = equal_value_res['equal_line_value']
f_plot = insert_data.loc[:, ['f']].values.reshape(n_grid, n_grid)
grid_y_plot, grid_x_plot = np.meshgrid(grid_y, grid_x)
plt_msg = contour_line_plot(grid_x_plot, grid_y_plot, f_plot, equal_value_list,x_long,y_long,n_group)
#data = data.set_index(axis.index)
if equal_value_res['gap_flag'] == False:
equal_value_list = [insert_data.loc[:, ['f']].min()[0]-1, insert_data.loc[:, ['f']].min()[0]]
res = {
# 等值线图
'plt_msg': plt_msg, # 等值线图数据流
'equal_value_list': equal_value_list, # 间距，标签
'xy_msg': [(min_x, max_x), (min_y, max_y)], # 边界坐标
'plot_data': data, # 绘图点数据
'plot_size': [x_long, y_long]
}
return res
if __name__ == "__main__":
res = contour_line([[5, 5, 11], [5, 25, 21], [10, 25, 45], [10, 5, 5], [8, 5, 60]], 5)
总结
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
