Python的Matplotlib绘图顺序错误

Question

基本上我有两个数组，一个包含x轴的值，第二个包含y轴的值。问题是，当我这样做时

plt.semilogy(out_samp,error_mc)

我明白了

哪个没有任何意义。这是因为绘图函数绘制了在x数组中遇到的所有内容，而不是关心它是否按升序排序。我如何对这两个数组进行排序，以便通过增加值对y数组进行排序，并以相同的方式对y轴进行排序，使得这些点相同但是连接的图是为了使它不会造成这种混乱？

提前谢谢！

Answer 1

在绘图之前按x轴的值排序。这是一个MWE。

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对于小数据，zip（如其他回答者所述）就足够了。

import itertools

x = [3, 5, 6, 1, 2]
y = [6, 7, 8, 9, 10]

lists = sorted(itertools.izip(*[x, y]))
new_x, new_y = list(itertools.izip(*lists))

# import operator
# new_x = map(operator.itemgetter(0), lists)        # [1, 2, 3, 5, 6]
# new_y = map(operator.itemgetter(1), lists)        # [9, 10, 6, 7, 8]

# Plot
import matplotlib.pylab as plt
plt.plot(new_x, new_y)
plt.show()

结果，

Answer 2

zip，排序和取消zip两个数据列表会更容易。

示例：

xs = [...]
ys = [...]

xs, ys = zip(*sorted(zip(xs, ys)))

plot(xs, ys)

请参阅此处的zip文档：https://docs.python.org/3.5/library/functions.html#zip

Answer 3

对列表进行排序的另一种方法是使用NumPy数组并使用np.sort()进行排序。使用数组的优点是在计算类似y = f（x）的函数时进行向量化操作。以下是绘制正态分布的示例：

不使用排序的数据

mu, sigma = 0, 0.1
x = np.random.normal(mu, sigma, 200)
f = 1/(sigma * np.sqrt(2 * np.pi)) *np.exp( - (x - mu)**2 / (2 * sigma**2) )
plt.plot(x,f, '-bo', ms = 2)

输出1

使用np.sort（）可以在计算正态分布时直接使用排序数组x。

mu, sigma = 0, 0.1
x = np.sort(np.random.normal(mu, sigma, 200)) 
# or use x = np.random.normal(mu, sigma, 200).sort()
f = 1/(sigma * np.sqrt(2 * np.pi)) *np.exp( - (x - mu)**2 / (2 * sigma**2) )
plt.plot(x,f, '-bo', ms = 2)

或者，如果您已经对x和y数据进行了未排序，则可以使用numpy.argsort对它们进行后验排序

mu, sigma = 0, 0.1
x = np.random.normal(mu, sigma, 200)
f = 1/(sigma * np.sqrt(2 * np.pi)) *np.exp( - (x - mu)**2 / (2 * sigma**2) )
plt.plot(np.sort(x), f[np.argsort(x)], '-bo', ms = 2)

在两种情况下，输出均为

输出2

Answer 4

您可以将数组转换为numpy数组，然后在第一个数组上使用argsort，获取数组并使用argsort数组对这两个数组进行排序。

Answer 5

就这样做

list=zip(*sorted(zip(*(x,y))))
plt.plot(*list)

排序函数将根据第一个参数排序，即x值

Answer 6

我认为您需要对一个数组进行排序，另一个数组也应该根据第一个数组进行排序。我从其他堆栈溢出问题得到了这个解决方案。最有可能这应该是你的解决方案。

out_samp,error_mc=zip(*sorted(zip(out_samp,error_mc)))

现在绘制这两个值，你得到一个正确的图形。