Draw lines from x axis and y axis to points

I want to draw the line from the point to the x and y axis:

Here is the code I used:

from sklearn.decomposition import PCA
pca = PCA()
principalComponents = pca.fit_transform(x)
plt.figure()
plt.plot(np.cumsum(pca.explained_variance_ratio_))
plt.xlabel('Number of Components')
plt.ylabel('Variance (%)') #for each component
plt.title('Explained Variance')

plt.show()
pca = PCA(n_components=0.8)
new_data = pca.fit_transform(x)
pca.explained_variance_ratio_
variance = np.cumsum(np.round(pca.explained_variance_ratio_, decimals=3))
variance
print(abs( pca.components_ ))

Here is the result:

Here's an example of what I'm talking about. Note that I start with the points of the graph, then I "post process" that by adding the additional lines.

import matplotlib.pyplot as plt

points = [(0,0), (2,1), (4,3), (6,4)]
xx = 
 for p in points]
yy = 
 for p in points]
plt.xlabel('Number of Components')
plt.ylabel('Variance (%)')
plt.title('Explained Variance')
plt.plot(xx,yy)
for c,(x,y) in enumerate(points):
    xx = [0, x, x]
    yy = [y, y, 0]
    plt.plot(xx,yy)

plt.show()

"Why", you may ask, "did you use enumerate to get a variable you don't use?" Because I thought I would need that to index into an array of colors. Here, I'm just relying on the matplotlib defaults for additional lines.

Output:

You could draw the lines using annotations.

1. find the values of the point (x, y) in relative axis-units (xa, ya)
2. draw annotation lines from the point (x, y) to the axis-boundaries (xa, 0) and (0, ya)

(note that they will NOT correctly update on zoom... this is also possible but requires a bit more work)

import matplotlib.pyplot as plt
import numpy as np

points = np.array([(0,0), (1,1), (2, 4)])

f, ax = plt.subplots()
ax.plot(*points.T)

def add_lines(points):
    f.canvas.draw()      # trigger a draw to make sure transformations are correct
    
    for x, y in points:
        # transform coordinates into relative axis-units (e.g. 0-1)
        xa, ya = ax.transAxes.inverted().transform(ax.transData.transform((x, y)))
        
        # add annotation-lines from the point to the x-axis
        ax.annotate(
            xy=(x, y), xycoords="data",
            xytext=(xa,0), textcoords="axes fraction",
            text="",
            arrowprops=dict(arrowstyle="-", shrinkA=0, shrinkB=0, color="r"),
            )
        # add annotation-lines from the point to the y-axis
        ax.annotate(
            xy=(x, y), xycoords="data",
            xytext=(0,ya), textcoords="axes fraction",
            text="",
            arrowprops=dict(arrowstyle="-", shrinkA=0, shrinkB=0, color="g")
            )

add_lines(points)