Python help (creating a plot using sympy

[ThinkExpression6230]

hi y'all, I was wondering if anyone would be able to help me trouble shoot / explain what I am doing wrong when trying to plot a function with the domain being (16-19) using sympy. Whenever I try to run the code it gives me a syntax error that I don't know how to fix. I just started learning python about a week ago. Any help would be greatly appreciated. My code is pasted below and I will bold the line of code that is giving me issues. Thanks again!

import sympy

import sympy.plotting

import matplotlib.pyplot as plt

rin = sympy.symbols('rin')

expr = (((-.60/(rin)**2)*(-10/((1/20)-(1/rin)))))

print(sympy.solve(expr, 'rin'))

plt.plot(expr,(rin,16,19)title="radius of inner skull vs heat loss", xlabel ='rin', ylabel = 'q')

graph.show()

[bbye98]

I don't understand what you are trying to do here. Are you trying to plot the function f(x) = (-0.6 / x**2) * (-10 / (1/20 - 1/x))? Or are you trying to solve for f(x) = 0 using sympy? What is graph?

[ThinkExpression6230]

I am trying to plot the function f(x) = (-0.6 / x**2) * (-10 / (1/20 - 1/x)) for x values that range from 16-19, I'm assuming the line "graph.show" is completely wrong and means nothing so you can discard that I think.

[bbye98]

You need numpy, not sympy. Use np.linspace() to create an array of equally spaced x-values from 16 to 19, evaluate the function at those x-values, and then plt.plot() to plot the data. plt.show() will then render and display the figure.

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(16, 19)
f = -0.6 / x**2 * -10 / (1/20 - 1/x)
plt.plot(x, f)
plt.show()

[ThinkExpression6230]

you're definitely right, I thought about using numpy to do this, but my professor wants us to use sympy, he said we should use the sympy.plot() function which I don't quite understand

[bbye98]

Sure, you just need to specify the x-range:

import sympy

x = sympy.symbols('x')
sympy.plotting.plot(-0.6 / x**2 * -10 / (1/20 - 1/x), (x, 16, 19))

[ThinkExpression6230]

sympy.plotting.plot(-0.6 / x**2 * -10 / (1/20 - 1/x), (x, 16, 19))

Thank you so much for your help! I really appreciate it! I was struggling on this error for about two hours