matplotlib triplot 和 tricontourf

Question

我正在尝试使用 tricontourf 在 matplotlib 中绘制具有非结构化坐标的二维数据集。我可以用 triplot 生成 'mesh' 的图，但是当我对 tricontourf 使用相同的 Triangulation 对象时，我得到一个错误（见下文）。我错过了什么？示例：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt

def lower(x):
    return 2 + 1*x

def upper(x):
    return 60 + 4*x

ni = 10
nj = 12

x = np.linspace(1,15,ni)

## make a trapezoid
xy = np.zeros((ni,nj,2),dtype=np.float32)
for i in range(len(x)):
    y = np.linspace(lower(x[i]),upper(x[i]),nj)
    xy[i,:,0] = x[i]
    xy[i,:,1] = y

## add noise
xy += -0.1 + 0.2*np.random.rand(ni,nj,2)

## make tris 'indices list'
xi, yi    = np.meshgrid(range(ni), range(nj), indexing='xy')
inds_list = np.stack((xi,yi), axis=2)
inds_list = np.reshape(inds_list, (ni*nj,2), order='C')
inds_list = np.ravel_multi_index((inds_list[:,0],inds_list[:,1]), (ni,nj), order='C')
inds_list = np.reshape(inds_list, (ni,nj), order='F')

tris = np.zeros((2*(ni-1)*(nj-1),3), dtype=np.int64)
ci=0
for i in range(ni-1):
    for j in range(nj-1):
        tris[ci,0] = inds_list[i+1, j+1]
        tris[ci,1] = inds_list[i,   j+1]
        tris[ci,2] = inds_list[i,   j  ]
        ci+=1
        tris[ci,0] = inds_list[i,   j  ]
        tris[ci,1] = inds_list[i+1, j  ]
        tris[ci,2] = inds_list[i+1, j+1]
        ci+=1

triangulation = mpl.tri.Triangulation(x=xy[:,:,0].ravel(), y=xy[:,:,1].ravel(), triangles=tris)

fig1 = plt.figure(figsize=(4, 4/(16/9)), dpi=300)
ax1 = plt.gca()
ax1.triplot(triangulation, lw=0.5)
#ax1.tricontourf(triangulation)
fig1.tight_layout(pad=0.25)
plt.show()

...产生

但是，取消注释带有 ax1.tricontourf

的行

抛出错误：

Traceback (most recent call last):
  File "test.py", line 54, in <module>
    ax1.tricontourf(triangulation)
  File "C:\Users\steve\AppData\Roaming\Python\Python38\site-packages\matplotlib\tri\tricontour.py", line 307, in tricontourf
    return TriContourSet(ax, *args, **kwargs)
  File "C:\Users\steve\AppData\Roaming\Python\Python38\site-packages\matplotlib\tri\tricontour.py", line 29, in __init__
    super().__init__(ax, *args, **kwargs)
  File "C:\Users\steve\AppData\Roaming\Python\Python38\site-packages\matplotlib\contour.py", line 812, in __init__
    kwargs = self._process_args(*args, **kwargs)
  File "C:\Users\steve\AppData\Roaming\Python\Python38\site-packages\matplotlib\tri\tricontour.py", line 45, in _process_args
    tri, z = self._contour_args(args, kwargs)
  File "C:\Users\steve\AppData\Roaming\Python\Python38\site-packages\matplotlib\tri\tricontour.py", line 60, in _contour_args
    z = np.ma.asarray(args[0])
IndexError: list index out of range

我正在使用：

Python版本：3.8.9

matplotlib 版本：3.5.1

Answer 1

我会说你需要为等高线提供值数组，例如：

x= xy[:,:,0].ravel()
z= np.random.rand(x.shape[0])
ax1.tricontourf(triangulation, z)

matplotlib triplot 和 tricontourf

matplotlib triplot and tricontourf

python

numpy

matplotlib