x1, x2, y1, y2 = ax.axis()
x1 = min(x_normalised) - 1
x2 = max(x_normalised) + 1
ax.axis((x1, x2, y1 - 1, y2 + 1))
nonRepetitive_x.insert(0, x[0] - 1)
nonRepetitive_x.append(x[-1] + 1)
How to assign equal scaling on the x-axis in Matplotlib?