Issue
I am a beginner in python and we currently have a required assessment that involves conic sections and matplotlib and I am trying to make a code that accepts user inputs(eg.The equation) and using those inputs it then outputs a graph of the input.
Here is my progress so far:
import sympy as sp
import matplotlib.pyplot as plt
import numpy as np
raw_expression = input("Enter the equation here:")
h = int(input("Please input the h value:"))
k = int(input("Please input the k value:"))
denominator1 = int(input("Please input the first denominator value:"))
denominator2 = int(input("Please input the second denominator value:"))
if denominator1 > denominator2:
denominator1 = a_squared
denominator2 = b_squared
else:
denominator2 = a_squared
denominator1 = b_squared
center_tuple = ()
vertice_tuple =()
center_tuple = center_tuple + (h,)
center_tuple = center_tuple + (k,)
a = sp.sqrt(a_squared)
b = sp.sqrt(b_squared)
vertice_tuple = vertice_tuple + (a,)
vertice_tuple = vertice_tuple + (b,)
x,y,z = sp.symbols('x,y,z',real=True)
expr = raw_expression
expr
def f(x,y): return (((x-h)**2)/denominator1) + (((y-k)**2)/denominator2) - 1
def calculate_points (cpoint, radius):
h, k = cpoint
a, b = radius
print("Right-most point (", h + a, ",", k,")" )
print("Left-most point (", h - a, ",", k,")" )
print("Top-most point (", h ,",", k + b,")" )
print("Bottom-most point (", h ,",", k - b,")" )
calculate_points(center_tuple,vertice_tuple)
Rmp= h + a
Lmp= h - a
Tmp= k + b
Bmp= k - b
Rmp= float(Rmp)
Lmp= float(Lmp)
Tmp= float(Tmp)
Bmp= float(Bmp)
x = np.linspace(Lmp,Rmp,1000)
y = np.linspace(Bmp,Tmp,1000)
x,y = np.meshgrid(x,y)
z = f(x,y)
fig, ax= plt.subplots()
ax.spines['bottom'].set_position('zero')
ax.spines['left'].set_position('zero')
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')
ax.contour(x,y,z,[0])
plt.scatter(h + a, k)
plt.scatter(h - a, k)
plt.scatter(h, k + b)
plt.scatter(h, k - b)
plt.axhline(0, alpha =.1)
plt.axvline(0, alpha=.1)
plt.show()
I am really troubled because it keeps spitting out errors and there was one time it worked but the graph was incorrect.
edit: Someone asked for an image of the expected output and it looks like this: Expected Output
but I also want the axes to be centered like this: Centered Axes
Solution
An ellipse can be drawn in different ways, I'll leave to the OP to find the relationship between the parameter they used and what I am using in the following code.
In [126]: from matplotlib.pyplot import show, subplots
...: from numpy import cos, linspace, pi, sin
...:
...: fig, ax = subplots(layout='constrained')
...: xc, yc = 0.5, -0.5
...: a, b = 2, 5
...: # Move the left and bottom spines to x = 0 and y = 0, respectively
...: ax.spines[["left" ]].set_position(("data", 0))
...: ax.spines[["bottom"]].set_position(("data", 0))
...: # Hide the top and right spines.
...: ax.spines[["top", "right"]].set_visible(False)
...: ax.plot(1, 0, ">k", transform=ax.get_yaxis_transform(), clip_on=False)
...: ax.plot(0, 1, "^k", transform=ax.get_xaxis_transform(), clip_on=False)
...: ax.set_aspect(1)
...:
...: θ = linspace(0, 2*pi, 629)
...: ax.plot(xc+a*cos(θ), yc+b*sin(θ))
...: ax.set_xlim((xc-1.5*a, xc+1.5*a)) ; ax.set_ylim((yc-1.5*b, yc+1.5*b))
...: for x, y, name in zip(
...: (xc, xc+a, xc, xc-a, xc,),
...: (yc, yc, yc+b, yc, yc-b,),
...: 'O A B C D'.split()):
...: label = '%s=(%s,%s)'%(name,x,y)
...: ax.scatter(x, y, label=label)
...: fig.legend()
...: show()
Answered By - gboffi
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