As a MatplotLib expert, you are asked to optimize a Python plotting script to make the plotted chart more complex. The script will be used to generate charts for a mathematical skill test. In order to test the ability to judge the data in the chart, specific data values cannot appear in the chart, so you should made a little more challenging. 
 
This is the code you need to optimize: 
```python 
{code} 
```  
Here's what I'd like you to do to optimize the chart: {direction} 
Now, let's take this task step by step. First, please read the given code carefully and analyze the chart it draws. Then, think about your optimization ideas with the given directions. 
In this step, you don't need to give the final code, only show the design ideas.