[In this line](https://github.com/tannerjt/classybrew/blob/master/src/classybrew.js#L351) in the second condition you want to check that `i+1 < length`. But if one of breaks is exactly equal to zero, this check will fail (and `lalse` will be returned).
Maybe, just check `i+1 < this.range.length`?
Test case:
```
var brew = new classyBrew();
brew.setSeries([10, 15, 20]);
brew.setNumClasses(3);
brew.setColorCode('BuGn');
brew.classify('equal_interval');
console.log(brew.getColorInRange(9)); //returns false - that's right
console.log(brew.getColorInRange(21)); //returns undefined - is this a bug? should return false too
```