title: how to make arrow thinner matplotlib
body: <p>I plot an arrow as below, whilst I think it's a little bit big. How can I make it thinner and smaller? Thank you</p>
  
  <pre><code>for i in range(len(x)):
      plt.annotate(df.index[i],xy=(x[i],y[i]),xytext=(x[i]+1.31,y[i]-0.55),arrowprops=dict(facecolor='blue', shrink=0.1))
  </code></pre>