Python Forum

Hi everyone!

I'm trying to represent some data with matplotlib. For this particular set, I need to compare only two data, each composed of a mean + error bars. Problem is, as there is only two x "points", they are represented at each ends of the x axis, and I can't find how to position them better (see attachment for graph).
Do you know how I could better center the x points?

NB: I'm a doctoral student in biology and barely know coding, so please excuse the messy code.

Thank you in advance!!

import matplotlib.pyplot as plt
import numpy as np


#upper, lower, estimate
MKPU=[7.05E-07,3.85E-07,5.37E-07]
MKPUR175=[1.77E-06,1.03E-06,1.37E-06]

data=[MKPU,MKPUR175]

mut_rates=[MKPU[2],MKPUR175[2]]
x=[1,2]
errors_low=[MKPU[1],MKPUR175[1]]
errors_up=[MKPU[0],MKPUR175[0]]

errors_low_calc=[]
errors_up_calc=[]
for i in range(len(errors_low)):
    errors_low_calc.append(mut_rates[i]-errors_low[i])

for j in range(len(errors_low)):
    errors_up_calc.append(errors_up[j]-mut_rates[j])

errors_calc=[errors_low_calc,errors_up_calc]



pvalue=[1.00E+00,5.7627E-06]

def convert_pvalue_to_asterisks(pvalue):
    if pvalue <= 0.001:
        return "***"
    elif pvalue <= 0.01:
        return "**"
    elif pvalue <= 0.05:
        return "*"
    return "ns"

asterisks=[]

for j in range(0,len(pvalue)):
    a=convert_pvalue_to_asterisks(pvalue[j])
    asterisks.append(a)


plt.figure(figsize=(3,5))

plt.errorbar(x,mut_rates,yerr=errors_calc,fmt='or',capsize=5,ecolor='black')
#fmt: https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.plot.html#matplotlib.pyplot.plot

plt.xticks(x,('MKPU','MKPUR175'))


for i in range(1,len(asterisks)):
    x1, x2 = 1, i+1
    y, h, col = max(map(max,data)) + 1E-07, 6E-08*i, 'k'
    plt.plot([x1, x1, x2, x2], [y, y+h, y+h, y], lw=1.5, c=col)
    plt.text((x1+x2)*.5, y+h, asterisks[i], ha='center', va='bottom', color=col)

plt.xlabel('p53 alleles',fontsize=15)
plt.ylabel('Inactivation frequency',fontsize=15)
plt.title('p53 CD alleles inactivation frequency',fontsize=18)

[attachment=3301]