I'm trying to plot the error function in the form:

```
#!/usr/bin/env python
import matplotlib.pyplot as plt
import numpy as np
import math
from scipy.special import erf
from scipy.integrate import quad
import scipy.integrate as integrate

def integrand(t, alpha, r ):
        return np.exp(-alpha*(t-r)**2)

def damp(alpha, rho, r):
        return quad(integrand, 0, rho, args=(alpha, r))[0]

def norm_constant(alpha, r):
        return 2.0*math.sqrt(2)/math.sqrt(math.pi) * (1./(1.- erf(-math.sqrt(np.abs(alpha))*r)))

A = 1.5
r = 0.3

g = [ norm_constant(A,r) *damp(A,x,r) for x in np.arange(-2,2,0.2)]
x = np.arange(-2,2,0.2)

A2 = 1.8
r2 = 0.3
g2 = [ norm_constant(A2,r2) *damp(A2,x,r2) for x in np.arange(-2,2,0.2)]
plt.plot(x,g,'r')
plt.plot(x,g2,'b')
plt.show()

```

I want to visualize how the error function changes when we play with Alpha and r. However, I am getting the error message in return:

```
  plt.plot(x,g,'r')
  File "/usr/local/lib/python2.7/site-packages/matplotlib/pyplot.py", line 3154, in plot
    ret = ax.plot(*args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/matplotlib/__init__.py", line 1812, in inner
    return func(ax, *args, **kwargs)
  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes/_axes.py", line 1424, in plot
    for line in self._get_lines(*args, **kwargs):
  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 386, in _grab_next_args
    for seg in self._plot_args(remaining, kwargs):
  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 364, in _plot_args
    x, y = self._xy_from_xy(x, y)
  File "/usr/local/lib/python2.7/site-packages/matplotlib/axes/_base.py", line 223, in _xy_from_xy
    raise ValueError("x and y must have same first dimension")
ValueError: x and y must have same first dimension

```

How can I accomplished my task?