Matplotlib output too small to read

Question

In adjusting the domain of a function to find certain parameters in a matplotlib plot, I found that when I try to isolate the part I need, the output becomes so small that details are impossible to see. I've tried refreshing the kernel with no change and plt.rcParams['figure.figsize'] hasn't been effective either.

This is my current code, with unused options in the function removed.

import numpy as np
import matplotlib.pyplot as plt

def P_cubic(V,T,Tc,Pc,ParamSet,omega=0):
    R = 8.31446261815324 #J mol^-1 K^-1
    
    Tr = T/Tc
    
    if ParamSet == 'vdW':
       
    elif ParamSet == 'RK':
        
    elif ParamSet == 'SRK':
       
    elif ParamSet == 'PR':
        alpha   = (1+(0.37464+1.54226*omega-0.26992*omega**2)*
                   (1-Tr**(1/2)))**2
        sigma   = 1+np.sqrt(2)
        epsilon = 1-np.sqrt(2)
        Omega   = 0.07780
        Psi     = 0.45724
        Zc      = 0.30740
    
    a   = Psi*alpha*R**2*Tc**2/Pc
    b   = Omega*T*Tc/Pc #m3 mol-1
    
    P = R*T/(V-b)-a/((V+epsilon*b)*(V+sigma*b))
    return P

Tc    = 512.5    #K
Pc    = 8.0840E6 #Pa
omega = 0.565831

T = 473 #K

b = 0.07780*T*Tc/Pc #m3 mol-1

V = np.arange(0,1,0.001)
Vrange = b*V #m3 mol-1

PPa = np.empty(len(Vrange))
for i in range(len(Vrange)):
    PPa[i]=P_cubic(Vrange[i],T,Tc,Pc,'PR',omega) #Pa

Pbar = PPa*1.0E-5 #bar

plt.rcParams['figure.figsize']=(1,0.8)
plt.plot(V,Pbar)
plt.xlabel('V/b')
plt.ylabel('P /bar')
plt.xlim(0,np.max(V))
plt.ylim(np.min(Pbar),np.max(Pbar))
plt.title('Variance of Pressure with Volume of Pure Methanol at 473 K')
plt.text(15,-6,f'b = {b:.2E} m^3/mol');

Below are screenshots with the output at varying figsize parameters to show that plt.rcParams['figure.figsize'] is not helping. How do I fix this so that I can see the details of the plot?

Does this answer your question? [How do you change the size of figures drawn with Matplotlib?](https://stackoverflow.com/questions/332289/how-do-you-change-the-size-of-figures-drawn-with-matplotlib) — Jody Klymak, Feb 22 '22 at 05:21

score 0 · Answer 1 · answered Feb 22 '22 at 03:28

There are two reasons for this. First, the size unit of the graph is inches, so the specified number itself is small, resulting in a smaller graph. Secondly, the default coordinates of the annotations are based on the data, so the x-value is 15, which is far from the graph, so the figure is automatically smaller. So, I think you need to set the graph size and fix the x-value of the annotations.

fig, ax = plt.subplots()
plt.rcParams['figure.figsize']=(8,4)
ax.plot(V,Pbar)
plt.xlabel('V/b')
plt.ylabel('P /bar')
plt.xlim(0,np.max(V))
plt.ylim(np.min(Pbar),np.max(Pbar))
plt.title('Variance of Pressure with Volume of Pure Methanol at 473 K')
plt.text(1.1,-6,f'b = {b:.2E} m^3/mol')
#plt.text(1.1,-6,f'b = {b:.2E} m^3/mol', transform=ax.transData)

plt.show()

Matplotlib output too small to read

1 Answers1