Adding secondary X-axis with user-defined list of coordinates

Question

I have a function for plotting amount of graphics using pyplot. The code is here:

def plot_results(results, expers):
    """
    type results: list[list[float]]
    type expers: list[int]
    """
    label_builder = lambda index: 'experiment ' + str(index + 1)
    colors = ('green', 'blue')
    x_indices = list(map(compute_filesize, list(range(np.shape(results)[1]))))
    x_percents = list(map(compute_percent, list(range(np.shape(results)[1]))))

    fig, ax1 = plt.subplots()
    for i in range(expers):
        ax1.plot(x_indices, results[i], color=colors[i], lw=2, label=label_builder(i))
    ax1.legend()
    plt.show()

For each value of expers list my function plots a chart. For example, if len(results) == len (expers) == 2, I will get such graph:

I need to create the secondary X-axis (similarly to this, but it may be X-axis and it will be located on the top of graph). Another difference is that I need to set list of coordinates manually (e.g. ax2.set_coords(x_percents)).

I created new axis using ax2 = ax1.twinx(). Then, I established coordinates list using ax2.set_xticks(x_percents).

But because of each x_percents[i] < x_indices[i], I got such picture:

(as you can see, all coordinates of new axis are located in left-bottom corner)

How can I change my function to make new X-axis:

• located on the top side of the graph,

• has its own scale, i.e. each value of x_percents corresponds to value of results[i] and x_percents dispersed throughout interval?

Answer 1

您的代码表明x_indices和x_percents是线性相关的。为了使事情清楚明白并对其他人有用，我将假设以下两个变量：

x_indices = [0, 5, 10, 25, 50]
max_size = max(x_indices)
x_percents = [ n/max_size * 100 for n in x_indices]

你可以通过一种方法来创建与相同数据相关的双轴，但只是有不同的标签，如下所示：首先创建一个轴，然后创建另一个 over （{{可以使用1}} / twinx方法但不是绝对必要的，为了方便起见，我将在这里使用它们，并解释导致您为第一个轴设置xticks的重要问题。然后确保两个x轴的极限相同，设置x刻度的位置与第一个轴相同，最后更改标签：

twiny

在物理学中经常遇到这样的图形，例如，波长和能量成反比。在一个轴上，您将能够以一个刻度（例如纳米）读取单位，而另一个轴将以不同的比例（例如电子伏特）表示相同的数据。