TypeError: 'float' object cannot be interpreted as an integer when running python  chaco/examples/demo/advanced/spec_waterfall.py

**Problem Description**
TypeError: 'float' object cannot be interpreted as an integer 

[Steps to reproduce issue here.]

```python
python  chaco/examples/demo/advanced/spec_waterfall,py
```

**Expected behavior:**
example past

**OS, Python version:** [MacOS, python3.8 with or without EDM, python3.11]
