Matplotlib clip or trim lines and polygon - numpy

Question

How can I efficiently "trim" or "clip" or remove the portion of the red line outside of the purple box? Is there a trick with numpy masks?
Using Python 3.8.3 and Matplotlib
x = [10,15.5,12.5,7.5,5,10]
y = [15,10,5,5,10,15]
fig, ax = plt.subplots()
ax.fill_between(x,y, facecolor="blue", alpha=0.25)
ax.axis("equal")
myinterval = 1.5
xvals = np.arange(min(x), max(x)+1, myinterval)
for i in xvals:
ax.plot([i,i], [0,20], color='red')

Answer 1

This is done not using numpy masks. If I understand correctly, this is the code:
fig, ax = plt.subplots()
x = [10,15.5,12.5,7.5,5,10]
y = [15,10,5,5,10,15]
ax.fill_between(x,y, facecolor="blue", alpha=0.25)
ax.axis("equal")
myinterval = 1.5
xvals = np.arange(min(x), max(x)+1, myinterval)
def generate_equation(x, y):
# y = mx + b
# b = y - mx
left = []
right = []
M = []
B = []
for i in range(len(x)-1):
m = ((y[i+1] - y[i]) / (x[i+1] - x[i]))
b = y[i+1] - m*x[i+1]
M.append(m)
B.append(b)
left.append(min(x[i], x[i+1]))
right.append(max(x[i], x[i+1]))
return M, B, left, right
M, B, left, right = generate_equation(np.array(x), np.array(y))
for i in range(len(xvals)):
ylim = []
for j in range(len(M)):
if xvals[i] >= left[j] and xvals[i] <= right[j]:
Y = M[j] * xvals[i] + B[j]
ylim.append(Y)
ax.vlines(xvals[i], min(ylim), max(ylim), 'r')
Output: