python - 无法使用 matplotlib 绘制图形

Question

我一直试图在网格上找到最短距离的两个点。我有2个问题：

1）我无法想出一个有效的算法来找到点之间的路径。

2）我正在处理4个不同的点。0是起点，1是障碍物，2是终点，3是访问过的点。我希望已访问的点变为红色。但是当我这样做时，超过一半的图表变成了红色。

这是我的代码：

import matplotlib as mpl
from matplotlib import pyplot
import numpy as np


grid = [[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [1,0,1,0,1,0,1,0,1,2,1,0,1,0,1,0,1,0,1,0],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
        [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
        [1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0],
    ]





def search(x, y):
    if grid[x][y] == 2:
        print ('found at %d,%d' % (x, y))
        return True
    elif grid[x][y] == 1:
        #print ('wall at %d,%d' % (x, y))
        return False
    elif grid[x][y] == 3:
        print ('visited at %d,%d' % (x, y))
        return False

    #print ('visiting %d,%d' % (x, y))

    # mark as visited
    grid[x][y] = 3

    # explore neighbors clockwise starting by the one on the right
    if ((x < len(grid)-1 and search(x+1, y))
        or (y > 0 and search(x, y-1))
        or (x > 0 and search(x-1, y))
        or (y < len(grid)-1 and search(x, y+1))):
        return True

    return False

search(0, 0)

zvals = grid

ax = pyplot.gca()
major_ticks = np.arange(0.5, 20, 1)
pyplot.xticks(rotation=90)
ax.set_xticks(major_ticks)
ax.set_yticks(major_ticks)
ax.grid(which='both')
pyplot.grid(True)

# make a color map of fixed colors
cmap = mpl.colors.ListedColormap(['white','black'])
bounds=[-2,-1,1,2]
norm = mpl.colors.BoundaryNorm(bounds, cmap.N)

# tell imshow about color map so that only set colors are used
img = pyplot.imshow(zvals,interpolation='nearest',
                    cmap = cmap,norm=norm)

# make a color bar
pyplot.colorbar(img,cmap=cmap,
                norm=norm,boundaries=bounds,ticks=[0,1])

pyplot.show()

标签： pythonmatplotlib

Answer 1

由于算法本身运行良好，我想唯一的问题是显示结果的正确性。我建议在网格上使用尽可能多的不同颜色，这里有 4 种不同的颜色。

# make a color map of fixed colors
cmap = mpl.colors.ListedColormap(['white','black','red','limegreen'])
bounds=[-.5,0.5,1.5,2.5,3.5]
norm = mpl.colors.BoundaryNorm(bounds, cmap.N)

# tell imshow about color map so that only set colors are used
img = pyplot.imshow(zvals,interpolation='nearest', norm=norm, cmap=cmap)

# make a color bar
pyplot.colorbar(img, ticks=list(range(4)))