用如下语句，得到volumn_qq_4.pdf图一张
df4=pd.DataFrame(df,columns=['gun1','gun2','gun3','gun4'])
#pd.scatter_matrix(df,alpha=.2,figsize=(6,6),diagonal='kde')
pd.scatter_matrix(df4,alpha=.2,figsize=(6,6),diagonal='kde')
但希望这个qq图中能有如volumn_qq.pdf的效果，即增加一条y=x的线,该图由以下代码画出
f = np.empty(len(v),dtype = np.float32)
v_sorted = np.empty(len(v),dtype = np.float32)
v_sorted = np.sort(v,axis=0)
N = len(v_sorted)
for i in range(N):#i from 0,to N-1
     f = (i+.5)/N
  
f2 = np.empty(len(v2),dtype = np.float32)
v2_sorted = np.empty(len(v2),dtype = np.float32)
v2_sorted = np.sort(v2,axis=0)
N2 = len(v2_sorted)
for i in range(N2):#i from 0,to N-1
     f2 = (i+.5)/N2
  
  
N_qq = min(N,N2)
  
v_qq = np.empty(N_qq,dtype = np.float32)
v2_qq = np.empty(N_qq,dtype = np.float32)
  
for i in range(N_qq):
    v_qq = v_sorted
    v2_qq = v2_sorted
  
#plt.scatter(f,v_sorted)
#plt.scatter(f2,v2_sorted)
plt.scatter(v_qq,v2_qq,color='b')#qq plot
def f(x):
     return x
xmax = np.max(v_qq)
xmax += 1
x = range(int(xmax))
plt.plot(np.array(x),f(np.array(x)),color='r',linewidth=3)#